Prepare for and practice interview questions from System One.

System One Interview Questions

System One Interview Guides

Machine Learning

How would you encode a categorical variable with thousands of distinct values

Encoding Categorical Features

Which model would perform better and why?

Booking Regression

How do we deal with the missing square footage data to construct our model

Missing Housing Data

How would we build a model to detect fraud and text customers to approve or deny fraudulent transactions

Bank Fraud Model

How would we know if we have enough data to create an accurate enough model?

One Million Rides

Data Structures & Algorithms

Given two sorted lists, write a function to merge them into one sorted list.

Merge Sorted Lists

Find the missing integer from a array of consequtive integers

Find the Missing Number

Write a function n_frequent_words that returns the top N frequent words and their frequencies, and state its run-time

Get Top N Frequent Words

Write a function to return the names and resume IDs for resumes whose IDs have not already been scraped

New Resumes

Minimum Change

Write a query to select the top 3 departments with at least ten employees and rank them according to the percentage of their employees making over 100K in salary.

Employee Salaries

Select the 2nd highest salary in the engineering department

2nd Highest Salary

Calculate the first touch attribution for each `user_id` that converted.

First Touch Attribution

Write a query to return the two students with the closest test scores and the score difference

Closest SAT Scores

Write a query to get the total three-day rolling average for deposits by day

Rolling Bank Transactions

Probability

First to Six

What is the probability that each subsequent card is larger than the previous drawn card when picking three cards from a shuffled deck of 500 cards

500 Cards

What is the probability that it's actually raining in Seattle?

Raining in Seattle

What is the probability that item X would be found on Amazon's website?

Found Item

Given three uniform(0,4) random variables, what is the probability that the median of them is greater than 3?

Median Probability

Data Modeling

Design a data warehouse for a new online retailer

Retailer Data Warehouse

Design a database schema for a Tinder-style dating app and discuss needed optimizations

Swiping App Design

System design for a digital classroom service.

Digital Classroom System Design

Use of foreign key constraints instead of BIGINTS

Foreign Key Constraints

Design a database for a stand-alone fast food restaurant

Fast Food Database

<p>Write a SQL query to select the 2nd highest salary in the engineering department.</p>

<p><strong>Note:</strong> If more than one person shares the highest salary, the query should select the next highest salary.</p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>employees</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>first_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>last_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>salary</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>department_id</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<p><code>departments</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>
</tbody>
</table>
<p><strong>Output:</strong></p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>salary</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>


<p>Given the <code>employees</code> and <code>departments</code> table, write a query to get the top 3 highest employee salaries by department. If the department contains less that 3 employees, the top 2 or the top 1 highest salaries should be listed (assume that each department has at least 1 employee). </p>

<p><em>Note: The output should include the full name of the employee in one column, the department name, and the salary. The output should be sorted by department name in ascending order and salary in descending order.</em> </p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>employees</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>first_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>last_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>salary</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>department_id</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<p><code>departments</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>
</tbody>
</table>
<p><strong>Output</strong>:</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>employee_nam</code>e</td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>department_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>salary</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>


Get the top 3 highest employee salaries by department

Top Three Salaries

<p>We’re given a table of bank transactions with three columns, <code>user_id</code>, a deposit or withdrawal value (determined if the value is positive or negative), and <code>created_at</code> time for each transaction.</p>

<p>Write a query to get the total three-day rolling average for deposits by day.</p>

<p><em>Note: Please use the format <code>&#39;%Y-%m-%d&#39;</code> for the date in the outout</em></p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>bank_transactions</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>user_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>created_at</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>transaction_value</code></td>
<td>FLOAT</td>
</tr>
</tbody>
</table>
<p><strong>Output:</strong></p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>dt</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>rolling_three_day</code></td>
<td>FLOAT</td>
</tr>
</tbody>
</table>


<p>Given a table of students and their SAT test scores, write a query to return the two students with the closest test scores with the score difference.</p>

<p>If there are multiple students with the same minimum score difference, select the student name combination that is higher in the alphabet. </p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>scores</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>student</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>score</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<p><strong>Output:</strong></p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>one_student</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>other_student</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>score_diff</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>


<p>Given two sorted lists, write a function to merge them into one sorted list.</p>

<p><em>Bonus: What’s the time complexity?</em></p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="n">list1</span> <span class="o">=</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">5</span><span class="p">]</span>
</span></span><span class="line"><span class="cl"><span class="n">list2</span> <span class="o">=</span> <span class="p">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">]</span>
</span></span></code></pre>

<p><strong>Output:</strong></p>

<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">merge_list</span><span class="p">(</span><span class="n">list1</span><span class="p">,</span><span class="n">list2</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">]</span>
</span></span></code></pre>


<p>You have two sorted lists, one with m elements and one with n elements. What would be the time complexity of merging the two lists via merge sort?</p>


You have two sorted lists, one with m elements and one with n elements. What would be the time complexity of merging the two lists via merge sort? 

Merging Lists Complexity

<p>Given a <code>employees</code> and <code>departments</code> table, select the top 3 departments with at least ten employees and rank them according to the percentage of their employees making over 100K in salary.</p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>employees</code> table</p>

<table>
<thead>
<tr>
<th>Columns</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>first_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>last_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>salary</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>department_id</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<p><code>departments</code> table</p>

<table>
<thead>
<tr>
<th>Columns</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>
</tbody>
</table>
<p><strong>Output:</strong></p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>percentage_over_100k</code></td>
<td>FLOAT</td>
</tr>

<tr>
<td><code>department_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>number_of_employees</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>


<p>Given a table called <code>employees</code>, get the largest salary of any employee by department</p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>employees</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>department</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>salary</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<p><strong>Output:</strong></p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>department</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>largest_salary</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>


Write a query to get the largest salary of any employee by department

Largest Salary by Department

<p>Let’s say you work at a file-hosting website. You have information on user’s daily downloads in the <code>download_facts</code> table</p>

<p>Use the window function <code>RANK</code> to display the top three users by downloads each day. Order your data by <code>date</code>, and then by <code>daily_rank</code></p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>download_facts</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>user_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>date</code></td>
<td>DATE</td>
</tr>

<tr>
<td><code>downloads</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<p><strong>Output:</strong></p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>daily_rank</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>user_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>date</code></td>
<td>DATE</td>
</tr>

<tr>
<td><code>downloads</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>


Write a query to display the top three users by downloads each day

Top 3 Users

<p>Let’s say that your company is running a standard control and variant AB test on a feature to increase conversion rates on the landing page. The PM checks the results and finds a .04 p-value.</p>

<p>How would you assess the validity of the result?</p>


How would you assess the validity of the result?

Experiment Validity

A/B Testing

<p>The schema below is for a retail online shopping company consisting of two tables, <code>attribution</code> and <code>user_sessions</code>.</p>

<ul>
<li><p>The attribution table logs a session visit for each row.</p></li>

<li><p>If <code>conversion</code> is <code>true</code>, then the user converted to buying on that session.</p></li>

<li><p>The <code>channel</code> column represents which advertising platform the user was attributed to for that specific session.</p></li>

<li><p>Lastly the <code>user_sessions</code> table maps many to one session visits back to one user.</p></li>
</ul>

<p>First touch attribution is defined as the channel with which the converted user was associated when they first discovered the website.</p>

<p>Calculate the first touch attribution for each <code>user_id</code> that converted. </p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>attribution</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>session_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>channel</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>conversion</code></td>
<td>BOOLEAN</td>
</tr>
</tbody>
</table>
<p><code>user_sessions</code> table</p>

<table>
<thead>
<tr>
<th>column</th>
<th>type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>session_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>created_at</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>user_id</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<p><strong>Example output:</strong></p>

<table>
<thead>
<tr>
<th><code>user_id</code></th>
<th><code>channel</code></th>
</tr>
</thead>

<tbody>
<tr>
<td>123</td>
<td>facebook</td>
</tr>

<tr>
<td>145</td>
<td>google</td>
</tr>

<tr>
<td>153</td>
<td>facebook</td>
</tr>

<tr>
<td>172</td>
<td>organic</td>
</tr>

<tr>
<td>173</td>
<td>email</td>
</tr>
</tbody>
</table>


<p>Given an integer <code>N</code>, write a function that returns a list of all of the prime numbers up to <code>N</code>.</p>

<p><em>Note: Return an empty list there are no prime numbers less than or equal to <code>N</code>.</em></p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="n">N</span> <span class="o">=</span> <span class="mi">3</span>
</span></span></code></pre>

<p><strong>Output:</strong></p>

<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">prime_numbers</span><span class="p">(</span><span class="n">N</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="p">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">]</span>
</span></span></code></pre>


Given an integer N, write a function that returns all of the prime numbers up to N

Prime to N

<p>Let’s say we’re comparing two machine learning algorithms. In which case would you use a bagging algorithm versus a boosting algorithm? </p>

<p>Give an example of the tradeoffs between the two.</p>


<p>In machine learning, when would you use a bagging algorithm over a boosting algorithm?</p>


In machine learning, when would you use a bagging algorithm over a boosting algorithm?

Bagging vs. Boosting

In which case would you use a bagging algorithm versus a boosting algorithm

Bagging vs Boosting

<p>Amy and Brad take turns in rolling a fair six-sided die. Whoever rolls a “6” first wins the game. Amy starts by rolling first.</p>

<p>What’s the probability that Amy wins?</p>


Amy and Brad take turns in rolling a fair six-sided die. Whoever rolls a “6” first wins the game. Amy starts by rolling first.

What’s the probability that Amy wins?

<p>Let’s say you’re working in HR at a major tech company, and they ask you to find employees with a high probability of leaving the company. They tell you these employees perform well but have the lowest pay.</p>

<p>Given two tables, <code>employees</code>  and <code>projects</code>, find the five lowest-paid employees who have completed at least three projects.</p>

<p>Note: We consider projects to be completed when they have an end date, which is the same as saying their <code>End_dt</code> is not <code>NULL</code>.</p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>employees</code> table</p>

<table>
<thead>
<tr>
<th>id</th>
<th>salary</th>
</tr>
</thead>

<tbody>
<tr>
<td>INTEGER</td>
<td>FLOAT</td>
</tr>
</tbody>
</table>
<p><code>projects</code> table</p>

<table>
<thead>
<tr>
<th>employee_id</th>
<th>project_id</th>
<th>Start_dt</th>
<th>End_dt</th>
</tr>
</thead>

<tbody>
<tr>
<td>INTEGER</td>
<td>INTEGER</td>
<td>DATETIME</td>
<td>DATETIME</td>
</tr>
</tbody>
</table>
<p><strong>Output:</strong></p>

<table>
<thead>
<tr>
<th>employee_id</th>
</tr>
</thead>

<tbody>
<tr>
<td>INTEGER</td>
</tr>
</tbody>
</table>


Find the five employees with the hightest probability of leaving the company

Top 5 Turnover Risk

<p>You are about to get on a plane to Seattle. You want to know if you should bring an umbrella. You call 3 random friends of yours who live there and ask each independently if it’s raining. Each of your friends has a <sup>2</sup>⁄<sub>3</sub> chance of telling you the truth and a <sup>1</sup>⁄<sub>3</sub> chance of messing with you by lying. All 3 friends tell you that “Yes” it is raining.</p>

<p>What is the probability that it’s actually raining in Seattle?</p>


<p>What is the <strong>main</strong> difference between the Frequentist and Bayesian methods of probabilistic analysis?</p>


What is the **main** difference between the Frequentist and Bayesian methods of probabilistic analysis?

Frequentist Vs Bayesian Analysis

<p>Let’s say you work at Allstate. Allstate is running <code>N</code>  online ads right now. The table <code>ads</code> contains all those ads, ranked by popularity via the <code>id</code> column (e.g., the entry with <code>id = 1</code> is the most popular, etc.).</p>

<p>Create a subquery or common table expression named <code>top_ads</code> containing the top 3 ads (by popularity) and return the number of rows that would result from the following operations</p>

<ol>
<li><code>ads INNER JOIN top_ads</code></li>
<li><code>ads LEFT JOIN top_ads</code></li>
<li><code>ads RIGHT JOIN top_ads</code></li>
<li><code>ads CROSS JOIN top_ads</code></li>
</ol>

<p><em>Note: Please make the <code>join_type</code> column in your output have the values <code>inner_join</code>, <code>left_join</code>, etc. for each of their respective join types</em></p>

<p><em>Note: Please return only one query with each number in a different row</em></p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>
</tbody>
</table>
<p><strong>Output:</strong></p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>join_type</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>number_of_rows</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>


Create top_ads with the top 3 ads and return the row counts for inner, left, right, and cross joins with ads

Size of Joins

<p>Let’s say you run a wine house. You have detailed information about the chemical composition of wines in a <code>wines</code> table.</p>

<p>One day, a customer comes asking specifically for a wine that has</p>

<ul>
<li>Greater or equal to than 13% alcohol content</li>
<li>Ash content less than 2.4</li>
<li>A color intensity less than 3</li>
</ul>

<p>Write a query to find the <code>id</code>s of suitable wines for this customer.</p>

<p><em>Note:</em> All percentages are reported with two numbers before the decimal point; for example, 13.55% is represented as <code>13.55</code> instead of <code>0.1355</code>.</p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>wines</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>alcohol</code></td>
<td>FLOAT</td>
</tr>

<tr>
<td><code>malic_acid</code></td>
<td>FLOAT</td>
</tr>

<tr>
<td><code>ash</code></td>
<td>FLOAT</td>
</tr>

<tr>
<td><code>alcalinity_of_ash</code></td>
<td>FLOAT</td>
</tr>

<tr>
<td><code>magnesium</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>total_phenols</code></td>
<td>FLOAT</td>
</tr>

<tr>
<td><code>flavanoids</code></td>
<td>FLOAT</td>
</tr>

<tr>
<td><code>nonflavanoid_phenols</code></td>
<td>FLOAT</td>
</tr>

<tr>
<td><code>proanthocyanins</code></td>
<td>FLOAT</td>
</tr>

<tr>
<td><code>color_intensity</code></td>
<td>FLOAT</td>
</tr>

<tr>
<td><code>hue</code></td>
<td>FLOAT</td>
</tr>

<tr>
<td><code>od280_or_od315_of_diluted_wines</code></td>
<td>FLOAT</td>
</tr>

<tr>
<td><code>proline</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<p><strong>Output:</strong></p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>


Let’s say you run a wine house. You have detailed information about the chemical composition of wines in a wines table.

SELECTive Wine Connoisseur

<p>Say you are tasked with designing a data mart or data warehouse for a new online retailer.</p>

<p>How would you design the system?</p>

<p><em>Note: Sketch a star schema to explain your design.</em></p>


<p>You have an array of integers, <code>nums</code> of length <code>n</code> spanning <code>0</code> to <code>n</code> with one missing. Write a function <code>missing_number</code> that returns the missing number in the array.</p>

<p><em>Note: Complexity of $O(n)$ required.</em></p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="n">nums</span> <span class="o">=</span> <span class="p">[</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">]</span> 
</span></span><span class="line"><span class="cl"><span class="n">missing_number</span><span class="p">(</span><span class="n">nums</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="mi">3</span>
</span></span></code></pre>


<p>Imagine a deck of 500 cards numbered from 1 to 500. If all the cards are shuffled randomly and you are asked to pick three cards, one at a time, what’s the probability of each subsequent card being larger than the previous drawn card?</p>


<p>Imagine a deck of 2000 cards numbered from 1 to 2000. If all the cards are shuffled randomly and you are asked to pick three cards, one at a time, what’s the probability of each subsequent card being larger than the previously drawn card?</p>


Imagine a deck of 2000 cards numbered from 1 to 2000. If all the cards are shuffled randomly and you are asked to pick three cards, one at a time, what's the probability of each subsequent card being larger than the previously drawn card?

2000 cards

<p>Tell me about a data project that didn’t go the way you expected. What did you set out to do, what surprised you, and how did you handle it?</p>


Describing a data project and its challenges

Hurdles In Data Projects

Behavioral

<p>How would you explain what a p-value is to someone who is not technical?</p>


<p>What does a p-value in a statistical test represent?</p>

What does a p-value in a statistical test represent?

P-value to a Layman I

<p>In a statistical test, how does a low p-value (less than 0.05) influence our decision about the null hypothesis?</p>

In a statistical test, how does a low p-value (less than 0.05) influence our decision about the null hypothesis?

P-value to a Layman II

Explain what a p-value is to someone who is not technical

P-value to a Layman

Statistics

<p>Over budget on a project is defined when the salaries, prorated to the day, exceed the budget of the project.</p>

<p>For example, if Alice and Bob both combined income make 200K and work on a project of a budget of 50K that takes half a year, then the project is over budget given 0.5 * 200K = 100K &gt; 50K.</p>

<p>Write a query to forecast the budget for all projects and return a label of <code>&#34;overbudget&#34;</code> if it is over budget and <code>&#34;within budget&#34;</code> otherwise.</p>

<p><em>Note: Assume that employees only work on one project at a time.</em></p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>employees</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>first_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>last_name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>salary</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>department_id</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<p><code>projects</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>title</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>state_date</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>end_date</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>budget</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<p><strong>departments</strong> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>
</tbody>
</table>
<p><code>employee_projects</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>project_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>employee_id</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<p><strong>Output:</strong></p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>title</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>project_forecast</code></td>
<td>VARCHAR</td>
</tr>
</tbody>
</table>


Write a query to forecast each project's budget and label it overbudget or within budget

Over-Budget Projects

<p>Let’s say you have a categorical variable with thousands of distinct values, how would you encode it?</p>


<p>Which method can be used to extract communities from large networks, that does not require a pre-determined number of clusters like K-means?</p>

Which method can be used to extract communities from large networks, that does not require a pre-determined number of clusters like K-means?

<p>Write a query to identify the manager with the biggest team size.</p>

<p>You may assume there is only one manager with the largest team size.</p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>employees</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>manager_id</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<p><code>managers</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>team</code></td>
<td>VARCHAR</td>
</tr>
</tbody>
</table>
<p><strong>Output:</strong></p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>manager</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>team_size</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>


Manager Team Sizes

<p>Given a table of <code>transactions</code> and <code>products</code>, write a function to get the <code>month_over_month</code> change in revenue for the year 2019. Make sure to round <code>month_over_month</code> to 2 decimal places.</p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>transactions</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>user_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>created_at</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>product_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>quantity</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<p><code>products</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>price</code></td>
<td>FLOAT</td>
</tr>
</tbody>
</table>
<p><strong>Output:</strong></p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>month</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>month_over_month</code></td>
<td>FLOAT</td>
</tr>
</tbody>
</table>


Write a function to get the month_over_month change in revenue for 2019 rounded to 2 decimal places

Month Over Month

<p>Given a table with event logs, find the top five users with the longest continuous streak of visiting the platform.</p>

<p><em>Note: A continuous streak counts if the user visits the platform at least once per day on consecutive days.</em></p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>events</code> table</p>

<table>
<thead>
<tr>
<th><code>Column</code></th>
<th><code>Type</code></th>
</tr>
</thead>

<tbody>
<tr>
<td><code>user_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>created_at</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>url</code></td>
<td>VARCHAR</td>
</tr>
</tbody>
</table>
<p><strong>Output:</strong></p>

<table>
<thead>
<tr>
<th><code>Column</code></th>
<th><code>Type</code></th>
</tr>
</thead>

<tbody>
<tr>
<td><code>user_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>streak_length</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>


Longest Streak Users

<p>Write a Python function called <strong><code>max_profit</code></strong> that takes a list of integers, where the i-th integer represents the price of a given stock on day i, and returns the maximum profit you can achieve by buying and selling the stock.</p>

<p>You may complete, at most, two complete buy/sell transactions to maximize profits on a stock.</p>

<p><strong>Input:</strong></p>

<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="n">prices</span> <span class="o">=</span> <span class="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">4</span><span class="p">]</span>
</span></span></code></pre>

<p><strong>Output:</strong></p>

<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="k">def</span> <span class="nf">max_profit</span><span class="p">(</span><span class="n">prices</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="mi">6</span>
</span></span></code></pre>

<p>Explanation:</p>

<pre><code>Buy on day 4 (price = 0) and sell on day 6 (price = 3): profit = 3 - 0 = 3.
Then buy again on day 7 (price = 1) and sell on day 8 (price = 4): profit = 4 - 1 = 3.
Total profit: 3 + 3 = 6.
</code></pre>


Find the maximum profit from at most two stock buy/sell transactions

Maximum Profit

<p>You’re given a string that may contain the characters <strong><code>{</code></strong>, <strong><code>}</code></strong>, <strong><code>[</code></strong>, <strong><code>]</code></strong>, <strong><code>(</code></strong>, and <strong><code>)</code></strong>.</p>

<p><strong>Task:</strong> Verify that the string is balanced. A balanced string is one where every opening character, <strong><code>{</code></strong>, <strong><code>[</code></strong>, or <strong><code>(</code></strong>, has a corresponding closing character, <strong><code>}</code></strong>, <strong><code>]</code></strong>, or <strong><code>)</code></strong>.</p>

<p>Write a function called <strong><code>is_balanced(string: str) -&gt; bool</code></strong> which verifies the balance of a string.</p>

<p><strong>Example:</strong></p>

<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="n">is_balanced</span><span class="p">(</span><span class="s1">&#39;(())[]</span><span class="si">{}</span><span class="s1">&#39;</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="kc">True</span>
</span></span></code></pre>

<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="n">is_balanced</span><span class="p">(</span><span class="s1">&#39;{([()</span><span class="si">{}</span><span class="s1">])()}&#39;</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="kc">True</span>
</span></span></code></pre>

<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="n">is_balanced</span><span class="p">(</span><span class="s1">&#39;</span><span class="si">{}</span><span class="s1">[]())&#39;</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="kc">False</span>
</span></span></code></pre>

<hr/>


Write a function that tests whether a string of brackets is balanced.

The Brackets Problem

<p>Let’s say we have two tables, <code>transactions</code> and <code>products</code>. Hypothetically the <code>transactions</code> table consists of over a billion rows of purchases bought by users.</p>

<p>We are trying to find paired products that are often purchased together by the same user, such as wine and bottle openers, chips and beer, etc..</p>

<p>Write a query to find the top five paired products and their names.</p>

<p><em>Notes:</em>
   <em>For the purposes of satisfying the test case, p2 should be the item that comes first in the alphabet.</em>
   <em>The <code>qty</code> column represents paired products count</em></p>

<p><strong>Example:</strong></p>

<p><strong>Input:</strong></p>

<p><code>transactions</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>user_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>created_at</code></td>
<td>DATETIME</td>
</tr>

<tr>
<td><code>product_id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>quantity</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>
<p><code>products</code> table</p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>id</code></td>
<td>INTEGER</td>
</tr>

<tr>
<td><code>name</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>price</code></td>
<td>FLOAT</td>
</tr>
</tbody>
</table>
<p><strong>Output:</strong></p>

<table>
<thead>
<tr>
<th>Column</th>
<th>Type</th>
</tr>
</thead>

<tbody>
<tr>
<td><code>p1</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>p2</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>qty</code></td>
<td>INTEGER</td>
</tr>
</tbody>
</table>


Paired Products

Challenge

<h3>Job Description</h3><div>Job Description<div><p>LOCATION: Huntsville, AL (100% onsite)<b> TYPE: Contract-to-hire | 40 hrs/week<b> COMPENSATION: $62-67/hr (W2)<b> CLEARANCE: Active Secret clearance (or ability to obtain)<b> <b> OVERVIEW<b> System One is hiring a Software Engineer with strong C/C++ experience to support mission-critical defense/tactical software. You’ll help build and sustain software products such as analysis tools/simulations, mission-planning applications, and components used in operational systems. This role is onsite in Huntsville and supports programs with government stakeholders.<b> <b> WHAT YOU’LL DO -</b></b></b></b></b></b></b></b></p><ul><li>Contribute to full lifecycle software development (design, implementation, test, integration, and support) </li><li>Develop and maintain C/C++ software for complex, safety/security-conscious environments </li><li>Support <span class="long-word">architecture/design</span> discussions and implement scalable, maintainable solutions </li><li>Participate in technical reviews and code reviews to uphold quality and compliance </li><li>Work with cross-functional teams (systems, test, integration) and support end users as needed - </li><li>Assist with fielding, troubleshooting, and post-test/analysis activities - </li><li>Follow secure development and compliance requirements (cybersecurity/RMF and related standards) </li></ul><b> <b> REQUIRED QUALIFICATIONS - <b> Bachelor’s degree in a STEM/technical discipline (Software, CS, CE, EE, AE, Math, or similar) with GPA 3.0+ 2+ years of relevant software engineering experience <b> - Strong C/C++ development experience (must-have) <b> - Ability to work onsite in Huntsville, AL <b> - Active Secret clearance OR ability to obtain one <b> - Working knowledge of software engineering best practices (version control, coding standards, documentation, quality) <b> <b> NICE TO HAVE (PREFERRED) <b> - Python and/or Java experience <b> - Real-time or embedded systems experience; RTOS familiarity (VxWorks, FreeRTOS, etc.) <b> - Open systems / modular architectures (MOSA); frameworks like FACE, OMS, or SOSA <b> - <span class="long-word">Aerospace/defense/weapon</span> systems domain exposure <b> - Containerization, CI/CD <span class="long-word">(Docker/Kubernetes),</span> microservices - DO-178C, MIL-STD-882E, or similar standards experience <b> - MBSE / SysML; MATLAB/Simulink exposure <b> - Mission planning, navigation, sensors, or guidance & control concepts <p><b> </b></p><p>System One, and its subsidiaries including Joulé and Mountain Ltd., are leaders in delivering outsourced services and workforce solutions across North America. We help clients get work done more efficiently and economically, without compromising quality. System One not only serves as a valued partner for our clients, but we offer eligible employees health and welfare benefits coverage options including medical, dental, vision, spending accounts, life insurance, voluntary plans, as well as participation in a 401(k) plan.</p><p>System One is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender identity, age, national origin, disability, family care or medical leave status, genetic information, veteran status, marital status, or any other characteristic protected by applicable federal, state, or local law.</p><p>#M-1<b> Ref: #851-Rockville-S1</b></p><p><b></b></p></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></div></div>

<h3>Job Description</h3><div>Job Description<div><p><strong>Lead AI Software Engineer</strong><b> <strong>Employment Type:</strong> Contract-to-Hire<b> <strong>Clearance Requirement:</strong> Candidates must be eligible to obtain and maintain a Federal or DoD Public Trust. Approved adjudication is required before onboarding, and candidates with an active Public Trust or suitability determination are preferred.<b> <strong>Work Authorization:</strong> Candidates must be able to work in the United States without sponsorship.<b> <b> We are seeking a hands-on <strong>Lead AI Software Engineer</strong> to support the development of secure, scalable, and user-focused technology solutions for federal clients.<b> This role is ideal for a senior engineer who can lead the architecture and delivery of full-stack AWS applications while remaining actively involved in design, development, testing, deployment, and technical mentorship. You will work with software engineers, data scientists, product managers, and mission stakeholders to build modern applications that combine strong software engineering practices with Artificial Intelligence capabilities.<b> The position emphasizes full-stack engineering, cloud-native development, DevSecOps, accessibility, and the practical use of Generative AI tools to improve development velocity and software quality.<b> <strong>Key Responsibilities</strong></b></b></b></b></b></b></b></b></p><ul><li>Lead the architecture, design, development, and deployment of AI-enabled full-stack web applications in AWS.</li><li>Develop end-to-end solutions across ReactJS frontends, Java or Python backend services, APIs, workflow orchestration, and relational databases.</li><li>Design accessible and user-friendly web interfaces aligned with Section 508 and applicable usability standards.</li><li>Architect and maintain relational data models using technologies such as PostgreSQL, MySQL, or Amazon Aurora.</li><li>Build workflow orchestration and process automation capabilities supporting business and mission operations.</li><li>Develop dashboards, charts, analytics features, and interactive data visualization components.</li><li>Design and integrate AI-enabled capabilities such as intelligent search, chatbots, document processing, Retrieval-Augmented Generation, and agent-driven workflows.</li><li>Use Generative AI development tools such as GitHub Copilot, Cursor, Claude Code, or comparable platforms for coding, debugging, testing, refactoring, and documentation.</li><li>Ensure AI-assisted code meets established security, quality, maintainability, and compliance requirements.</li><li>Participate in a SAFe environment, including sprint planning, backlog refinement, Agile Release Trains, and cross-team coordination.</li><li>Implement DevSecOps practices and application security testing throughout the software development lifecycle.</li><li>Integrate SAST, DAST, SCA, container scanning, dependency scanning, automated testing, and compliance checks into CI/CD pipelines.</li><li>Mentor engineers, conduct code reviews, and establish best practices for software design, cloud development, security, and AI-enabled engineering.</li><li>Collaborate with technical and nontechnical stakeholders to prototype, iterate, and deliver solutions aligned with mission requirements.</li></ul><strong>Required Qualifications</strong><ul><li>Bachelor’s degree in Computer Science, Engineering, Data Science, or a related technical discipline.</li></ul> Four additional years of relevant professional experience may be considered in place of a degree. <ul><li>At least six years of professional software engineering experience, including experience in a senior, technical lead, or team leadership capacity.</li><li>Expert-level proficiency in either Java or Python for backend application development.</li><li>Strong hands-on experience developing modern frontend applications with ReactJS.</li><li>Demonstrated experience building and deploying full-stack applications in AWS.</li><li>Experience with workflow orchestration, process automation, relational databases, and data visualization.</li><li>Experience developing accessible web applications and working with accessibility standards or testing tools.</li><li>Strong experience designing and integrating RESTful APIs, microservices, and distributed systems.</li><li>Hands-on experience using Generative AI-assisted coding and software development tools.</li><li>Experience working within a SAFe or comparable scaled Agile environment.</li><li>Experience using DevSecOps and application security tools to identify, assess, and remediate software vulnerabilities.</li><li>Experience implementing CI/CD pipelines, automated testing, version control, and secure coding practices.</li><li>Strong leadership, communication, collaboration, and stakeholder-engagement skills.</li></ul><strong>Preferred Qualifications</strong><ul><li>Experience developing AI or Generative AI applications involving RAG, chatbots, semantic search, intelligent document processing, or agentic workflows.</li><li>Experience with LangChain, Haystack, Semantic Kernel, or similar AI application frameworks.</li><li>Hands-on experience with AWS services such as Lambda, ECS, Fargate, API Gateway, Step Functions, S3, Glue, or QuickSight.</li><li>Experience with modern data architectures, including lakehouse platforms, analytics environments, or federated query engines.</li><li>Experience with visualization technologies such as D3.js, Plotly, Tableau, or Amazon QuickSight.</li><li>Experience with Infrastructure as Code using Terraform, AWS CDK, or CloudFormation.</li><li>Familiarity with federal security and compliance frameworks such as FISMA, FedRAMP, or NIST 800-53.</li><li>SAFe, Agile, AWS, security, or related technical certifications.</li><li>Experience mentoring technical teams and driving the adoption of secure, AI-enabled, cloud-native engineering practices.</li></ul><p>System One, and its subsidiaries including Joulé and Mountain Ltd., are leaders in delivering outsourced services and workforce solutions across North America. We help clients get work done more efficiently and economically, without compromising quality. System One not only serves as a valued partner for our clients, but we offer eligible employees health and welfare benefits coverage options including medical, dental, vision, spending accounts, life insurance, voluntary plans, as well as participation in a 401(k) plan.</p><p>System One is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender identity, age, national origin, disability, family care or medical leave status, genetic information, veteran status, marital status, or any other characteristic protected by applicable federal, state, or local law.</p><p>#M1<b> #LI-CS1<b> Ref: #851-Rockville-S1</b></b></p><p><b></b></p></div></div>

<h3>Job Description</h3><div>Job Description<div><p><strong>Job Title</strong>: Data Analyst<b> <strong>Location</strong>: San Francisco, CA<b> <b> <strong>Type</strong>: Contract-to-Hire<b> <strong>Compensation:</strong> $25-$28/hour<b> <strong>Contractor Work Model</strong>: Onsite<b> <strong>Hours</strong>: Monday through Friday (8AM to 5PM)<b> </b></b></b></b></b></b></b></p><p><strong>DATA ANALYST</strong></p><p><b> <strong>SUMMARY:</strong><b> <b> Responsible for analyzing data and other information for the effective quality control and compliance management of the Housing Choice Voucher Program. Provide support to the HCV management team. This position may also include other duties, responsibilities, and project participation as assigned.<b> <b> <strong>RESPONSIBILITIES:</strong><b> </b></b></b></b></b></b></p><ul><li>Assists upper management & Lead Data Analyst with data analysis and program evaluation projects </li><li>Monitor accuracy of HAP Payment Processing </li><li>Assist with creating and/or deleting manual adjustments upon request </li><li>Collect data and create reports regarding program performance and quality control reviews </li><li>Assist with Quarterly Reconciliation process which includes gathering, dispersing, analyzing, and reviewing quarterly reconciliation reports </li><li>Review and monitor reports and/or documents and assign appropriate actions or corrective actions including but not limited to SEMAP, Enterprise Income Verification (EIV), PIH Information Center (PIC), 50058 error reports, HUD regulations, and the HCV administrative plan </li><li>Assist with monitoring Tracker to ensure record consistency </li><li>Set up monitor and maintain tools to support ongoing operations </li><li>Assist team with issues concerning caseload complications </li><li>Evaluate, investigate and work closely with management and supervisory staff to identify solutions to a variety of data related problems and issues </li><li>Coordinate with management to produce reports as required to ensure integrity of program data and provide ongoing monitoring of program operations </li><li>Monitor and manage PIC/EIV reports (Deceased; Multiply Subsidy et al) and ensure all <span class="long-word">corrections/adjustments</span> are made </li><li>Assist management with check run </li><li>Prepare reports for all levels of the organization and client this includes but are not limited to weekly New Admission reports, monthly delinquent Re-exam reports, and other reports as assigned </li><li>Monitor SEMAP Compliance on an ongoing basis and perform related Quality Control testing, file reviews, and data collection as necessary </li><li>All additional duties as assigned by supervisor </li></ul><b> <strong>QUALIFICATIONS:</strong> <b><ul><li>Bachelor’s degree PLUS one (1) year of similar relevant experience OR Minimum of 2–4 years’ experience working in a similar capacity </li><li>Proficient with current technology, computer hardware and software, easily grasps new software </li><li>Proficient in using database systems and analytical tools/instruments such as Microsoft Excel, Microsoft Access and SharePoint </li><li>Must possess an analytical mind able to process information logically </li><li>Able to work under critical time deadlines, re-evaluate priorities and interact well with all levels of personnel </li><li>Ability to effectively write memos and maintain documentation </li><li>Ability to operate necessary office equipment, computers and peripherals </li><li>Proficient in all areas of Microsoft Office Suite (Word, Excel, PowerPoint, Access, Outlook, etc.) and ability to create and manipulate and analyze data </li><li>Responsible for maintaining all required records and for the preparation of all required reports </li><li>Must have ability to safeguard confidential and sensitive information </li><li>Exercise sound and ethical judgment when acting on behalf of the organization </li></ul><p></p><p>System One, and its subsidiaries including Joulé and Mountain Ltd., are leaders in delivering outsourced services and workforce solutions across North America. We help clients get work done more efficiently and economically, without compromising quality. System One not only serves as a valued partner for our clients, but we offer eligible employees health and welfare benefits coverage options including medical, dental, vision, spending accounts, life insurance, voluntary plans, as well as participation in a 401(k) plan.<b> <b> System One is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender identity, age, national origin, disability, family care or medical leave status, genetic information, veteran status, marital status, or any other characteristic protected by applicable federal, state, or local law.<b> <b> #M1<b> </b></b></b></b></b></p><p><b> <b> Ref: #562-Joule Staffing - Edison</b></b></p><p><b></b></p></b></b></div></div>

<h3>Job Description</h3><div>Job Description<div><p>Job Title: Business Analyst - JD Edwards<b> Location: Winchester, Virginia, United States<b> Type: Contract To Hire<b> Responsibilities</b></b></b></p><ul><li>Support and enhance enterprise manufacturing and supply chain operations by acting as a liaison between business stakeholders, IT teams, and third-party vendors. </li><li>Analyze current business processes related to JD Edwards modules, Warehouse Management Systems (WMS), RF solutions, and logistics, identifying opportunities for optimization. </li><li>Gather, document, and validate business requirements, functional specifications, process flows, and use cases, creating BRDs, FDDs, Epics, and User Stories. </li><li>Provide functional expertise in JDE Supply Chain and Manufacturing modules, including Inventory Management, Procurement, Sales Order Management, Manufacturing, and WMS integrations. </li><li>Support and troubleshoot integrations between JDE, WMS platforms, RFSmart/RF solutions, EDI, and third-party logistics applications. </li><li>Collaborate with development, QA, and offshore teams during design, testing, and deployment activities, supporting Agile processes like backlog refinement, sprint planning, and user acceptance testing. </li><li>Facilitate workshops and requirement sessions with stakeholders, communicate project updates, risks, and dependencies, and support change management and user training activities. </li></ul> Requirements <ul><li>6+ years of experience supporting JD Edwards EnterpriseOne environments as a Business Analyst. </li><li>Strong functional expertise in JDE Supply Chain and Manufacturing modules. </li><li>Hands-on experience with Warehouse Management Systems (WMS) and RF-enabled warehouse operations. </li><li>Support experience with warehouse processes such as receiving, put-away, picking, packing, shipping, replenishment, and inventory control. </li><li>Understanding of WMS/JDE integrations and EDI transactions. </li><li>Experience in manufacturing and distribution environments. </li><li>Knowledge of Agile methodologies, Jira, and project delivery frameworks. </li><li>Excellent communication, analytical, and stakeholder management skills. </li><li>Experience working with offshore teams and cross-functional groups. </li></ul><p>System One, and its subsidiaries including Joulé and Mountain Ltd., are leaders in delivering outsourced services and workforce solutions across North America. We help clients get work done more efficiently and economically, without compromising quality. System One not only serves as a valued partner for our clients, but we offer eligible employees health and welfare benefits coverage options including medical, dental, vision, spending accounts, life insurance, voluntary plans, as well as participation in a 401(k) plan.</p><p>System One is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender identity, age, national origin, disability, family care or medical leave status, genetic information, veteran status, marital status, or any other characteristic protected by applicable federal, state, or local law.</p><p>#M-<b> #LI-</b></p><b> <b>Ref: #404-IT Pittsburgh<p><b></b></p></b></b></div></div>

<h3>Job Description</h3><div>Job Description<div><p><strong>Data Risk Analyst<b> Location: Pensacola, FL (Hybrid) <b> Pay Rate: $60/hr. W2. Benefits available<b> Position Type: Contract</b></b></b></strong><b> <b> Our client is seeking a detail-oriented and analytical Data Risk Analyst to join the Data Risk Governance team within the Human Resources (HR) Risk Office. In this role, you will help identify, assess, and mitigate risks related to data classification, data privacy, data quality, data use, and regulatory compliance. You will support the implementation of governance frameworks that ensure effective data risk management across the enterprise.<b> <b> <strong>Key Responsibilities:</strong></b></b></b></b></p><ul><li>Support the HR Manager and Managing Data Steward in assigned tasks related to established procedures, such as Data Transfer Authorizations. </li><li>Collaborate with business and IT stakeholders to identify data risks and recommend appropriate mitigation strategies. </li><li>Assist in the development and maintenance of data governance policies, standards, and procedures. </li><li>Monitor compliance with internal data policies and external regulatory requirements (e.g., Enterprise Data Governance and Information Security instructions and standards, GDPR, CCPA, HIPAA, etc.). </li><li>Support risk reporting by analyzing data and producing dashboards, scorecards, and executive summaries, as requested. </li><li>Participate in data incident investigations, root cause analyses, and remediation tracking. </li><li>Work with data stewards, data owners, legal, and compliance teams to promote awareness and accountability for data risk. </li><li>Maintain a register of data risks and control gaps and ensure timely follow-up and resolution. </li><li>Stay up-to-date on emerging data risks, industry best practices, and regulatory changes. </li><li>Contribute to continuous improvement of data risk documentation, assessments, and control evaluation processes. </li></ul><b> <strong>Qualifications:</strong><ul><li>Bachelor’s degree in Data Science, Risk Management, Information Systems, Business, or related field. </li><li>5+ years of experience in risk management, data governance, audit, or compliance; experience with data risk preferred. </li><li>Strong understanding of data risk concepts, including privacy, quality, security, and ethical use of data. </li><li>Familiarity with regulatory requirements such as GDPR, CCPA, SOX, or industry-specific standards. </li><li>Strong analytical mindset with proficiency in Excel, Power BI, Tableau, or similar tools. </li><li>Excellent communication and interpersonal skills; ability to translate complex issues for non-technical audiences. </li><li>Experience with GRC tools (e.g., Archer, OneTrust, LogicGate, ServiceNow) is a plus. </li><li>Ability to work independently and collaboratively in a fast-paced, evolving environment. </li></ul><b> <strong><span class="long-word">Preferred/Desirable</span> Certifications:</strong><ul><li>Certified Data Privacy Solutions Engineer (CDPSE) </li><li>Certified Information Privacy Professional (CIPP) </li><li>Certified Risk and Information Systems Control (CRISC) </li><li>DAMA Certified Data Management Professional (CDMP) </li><li>Experience with the organization's Policies and Procedures </li></ul><p><b> System One, and its subsidiaries including Joulé and Mountain Ltd., are leaders in delivering outsourced services and workforce solutions across North America. We help clients get work done more efficiently and economically, without compromising quality. System One not only serves as a valued partner for our clients, but we offer eligible employees health and welfare benefits coverage options including medical, dental, vision, spending accounts, life insurance, voluntary plans, as well as participation in a 401(k) plan.</b></p><p>System One is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender identity, age, national origin, disability, family care or medical leave status, genetic information, veteran status, marital status, or any other characteristic protected by applicable federal, state, or local law.</p><p>#M- MM1<b> #LI- MM1<b> Ref: #851-Rockville-S1</b></b></p><p><b></b></p></b></b></div></div>

<h3>Job Description</h3><div>Job Description<div><p>Job Title: Software Engineer Lead - Automation Anywhere<b> Location: Pittsburgh, PA<b> Type: Contract<b> Contractor Work Model: Onsite – onsite</b></b></b></p><p>Responsibilities</p><ul><li>Act as a tech lead to manage automation requests, determining suitable tools and platforms </li><li>Conduct meetings and discussions with multiple lines of business and the full team to coordinate actions and clarify requirements </li><li>Provide minimal mentoring to junior team members </li><li>Perform light coding tasks as needed </li></ul><p>Requirements</p><ul><li>8 - 10 years of experience in automation and development </li><li>Proficiency with Automation Anywhere, Microsoft Power Platform, Python or Java </li><li>Knowledge of Gen AI, SharePoint, Jira, or ServiceNow is a plus </li><li>Excellent communication skills, with the ability to explain technical concepts to non-technical audiences </li><li>Strong written and verbal communication skills </li><li>On-site work requirement at Strongsville, OH location </li></ul><p>System One, and its subsidiaries including Joulé and Mountain Ltd., are leaders in delivering outsourced services and workforce solutions across North America. We help clients get work done more efficiently and economically, without compromising quality. System One not only serves as a valued partner for our clients, but we offer eligible employees health and welfare benefits coverage options including medical, dental, vision, spending accounts, life insurance, voluntary plans, as well as participation in a 401(k) plan.</p><p>System One is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender identity, age, national origin, disability, family care or medical leave status, genetic information, veteran status, marital status, or any other characteristic protected by applicable federal, state, or local law.</p><p>#M-<b> #LI-<b> Ref: #404-IT Pittsburgh</b></b></p><p><b></b></p></div></div>

<h3>Job Description</h3><div>Job Description<div><p><strong>Job Title:</strong> Sr. Business Analyst<b> <strong>Location:</strong> St. Louis, Missouri<b> <strong>Type:</strong> Contract To Hire<b> <strong>Contractor Work Model:</strong> Onsite<b> <strong>Security Clearance:</strong> TS/SCI with ability to obtain polygraph within 90 days<b> <b> <strong>Responsibilities</strong></b></b></b></b></b></b></p><ul><li>Provide senior program and project management support, including the development of strategic plans, policies, and Standard Operating Procedures (SOPs). </li><li>Lead and advise on process improvement and re-engineering efforts, applying methodologies like Six Sigma and ITIL to modernize governance and business functions. </li><li>Craft and deliver executive-level briefings, talking points, and strategic project plans to guide senior leadership decisions. </li><li>Mentor team members on mission assurance, continuity planning, and the development of high-quality analytical products. </li><li>Provide expert-level support for data visualization tools like Tableau to support business functions and leadership requirements. </li><li>Support the design, development, and maintenance of SharePoint instances and other web-based tools, ensuring currency of information and refinement of utility. </li><li>Represent the directorate for User Interface (UI) development, coordinate with IT on corporate updates, and proactively address functionality issues. </li><li>Conduct in-depth analysis and assessment of metrics and data to provide actionable insights on organizational performance and strategic initiatives. </li><li>Assist in the creation, update, and implementation of organizational strategies, policies, and performance metrics to measure progress against goals. </li><li>Analyze, evaluate, and assess activities to develop recommendations for system and process improvements, optimization, and sustainment of GEOINT capabilities. </li><li>Establish performance measures, monitor metrics, and analyze results to identify and implement performance-based improvements. </li><li>Lead discussions at internal and external meetings, facilitate data-related working groups, and represent the organization to IC and DoD partners. </li></ul><b> <strong>Requirements</strong><ul><li>A minimum of a Bachelor’s degree in business, or a related field. </li><li>A minimum of 12+ years of experience in a relevant field such as program management, GEOINT/IC operations, or cross-functional business analysis. In lieu of a degree, 15+ years of experience. </li><li>Strong leadership competencies with proven experience leading and directing diverse teams to achieve high-performance outcomes, including mentoring team members in complex subject areas. </li><li>Exceptional skills in oral and written communication, with a demonstrated ability to present complex strategies, data, and operational metrics to senior leadership and external partners. </li><li>A proven track record of managing large-scale, cross-functional projects and initiatives, including risk management, resource allocation, and stakeholder engagement. </li><li>Proven ability to translate complex data into strategic recommendations for executive decision-makers and analyze the outcomes of implemented strategies. </li><li>Advanced knowledge of business application software for presentations, word processing, and SharePoint-based websites, with experience with data visualization tools (e.g., Tableau) highly desirable. </li><li>Relevant certifications (e.g., ITIL, Six Sigma, CMMI, ISO) required for certain positions. </li></ul><p><b> System One, and its subsidiaries including Joulé and Mountain Ltd., are leaders in delivering outsourced services and workforce solutions across North America. We help clients get work done more efficiently and economically, without compromising quality. System One not only serves as a valued partner for our clients, but we offer eligible employees health and welfare benefits coverage options including medical, dental, vision, spending accounts, life insurance, voluntary plans, as well as participation in a 401(k) plan.<b> <b> System One is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender identity, age, national origin, disability, family care or medical leave status, genetic information, veteran status, marital status, or any other characteristic protected by applicable federal, state, or local law.<b> <b> #M-2<b> #LI-CB5<b> Ref: #856-Baltimore-S1</b></b></b></b></b></b></b></p><p><b></b></p></b></div></div>

<h3>Job Description</h3><div>Job Description<div>Job Title: Business Analyst- RESTful API <b> Location: Dallas, Texas, United States <b> Job Type: Permanent Full Time <b> <b> Description: <b> <b> Business Analyst- RESTful API <b> <b> Position Description <b> We are seeking a skilled Business Analyst to support a backend engineering team that designs and builds RESTful APIs in a large e commerce environment supporting our client's customer facing applications. This role partners closely with Product Owners, Engineers, QE, and DevOps to translate business needs into clear, testable requirements that drive scalable, <span class="long-word">cloud?containerized</span> and cloud native services. <b> <b> <b> Your future duties and responsibilities <b> . Analyze business and technical requirements and write high quality user stories for backend RESTful services <b> . Define functional and non functional requirements, including performance, security, scalability, and observability <b> . Break down epics into well defined, testable stories with clear acceptance criteria including what can be automated for testing. <b> . Grasp upstream and downstream dependencies and system architecture to sequence work most efficiently <b> . Review and validate API contracts (OpenAPI/Swagger) to ensure clarity and alignment with business intent <b> . Support API testing and validation using tools like Postman <b> . Review logs, analyze and troubleshoot errors <b> . Participate in Agile ceremonies and support delivery through testing, defect triage, and release readiness <b> . Collaborate with backend engineers, QE, DevOps, and downstream partners across integrated systems <b> <b> <b> Required qualifications to be successful in this role <b> . Experience as a Business Analyst supporting backend or API centric teams <b> . Hands on experience with API testing and ability to understand API contracts is required <b> . Strong understanding of RESTful API design and integration patterns <b> . Working familiarity with AWS cloud concepts and services (e.g., API Gateway, Lambda, CloudWatch, IAM) <b> . Experience working in Agile/Scrum environments <b> . Strong analytical, documentation, and communication skills <b> . Curious mindset with ability to use AI tools with increasing efficiency <b> . Airline domain experience preferred <b><p><b></b></p></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></b></div></div>

<h3>Job Description</h3><div>Job Description<div><p><strong>Job Title: </strong>Senior Associate Research Scientist I<b> <strong>Location:</strong> Durham, NC<b> <strong>Type: </strong>Contract<b> <strong>Compensation:</strong> $30 - $35/hr<b> <strong>Work Model: </strong>Onsite</b></b></b></b></p><p><strong>Responsibilities</strong></p><ul><li>Provide analytical testing support for development and process characterization projects. </li><li>Perform analytical testing and analyses using modern instrumental analytical techniques, including Karl Fischer moisture analysis, coagulation assays, enzymatic assays, and immunoassays. </li><li>Operate and maintain analytical instruments such as coulometric titrator, coagulation analyzer, <span class="long-word">immunonephelometer,</span> and plate readers. </li><li>Document laboratory work accurately and contemporaneously in research notebooks or LIMS systems; contribute to report writing as needed. </li><li>Identify aberrant results, initiate investigations, and participate in problem-solving efforts independently. </li><li>Demonstrate strong organizational, attention to detail, and excellent verbal and written communication skills. </li><li>Maintain compliance with cGXP environment standards and regulatory guidance documents related to test methods and CMC development. </li><li>Perform moderate lifting of 15-30 lbs. with a maximum of 35 lbs., and work in an environment exposing to biological fluids, chemicals, and electrical equipment. </li></ul><strong>Requirements</strong><ul><li>Degree in Biology, Biochemistry, Chemistry, or Toxicology (Master’s preferred with 1+ years experience or Bachelor’s with 3-4 years relevant experience). </li><li>Relevant analytical test experience in a cGXP environment, including proper pipetting techniques and knowledge of regulatory guidance. </li><li>Experience operating and maintaining analytical instruments such as coulometric titrators, coagulation analyzers, <span class="long-word">immunonephelometers,</span> and plate readers. </li><li>Proficiency in MS Office applications. </li><li>Ability to perform detailed documentation and report writing. </li><li>Strong organizational, communication, and problem-solving skills. </li><li>Ability to work in a <span class="long-word">clinical/laboratory</span> environment with exposure to biological fluids, chemicals, and electrical equipment. </li></ul><p>System One, and its subsidiaries including Joulé and Mountain Ltd., are leaders in delivering outsourced services and workforce solutions across North America. We help clients get work done more efficiently and economically, without compromising quality. System One not only serves as a valued partner for our clients, but we offer eligible employees health and welfare benefits coverage options including medical, dental, vision, spending accounts, life insurance, voluntary plans, as well as participation in a 401(k) plan.</p><p>System One is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender identity, age, national origin, disability, family care or medical leave status, genetic information, veteran status, marital status, or any other characteristic protected by applicable federal, state, or local law.</p><p><b> Ref: #558-Scientific</b></p><p><b></b></p></div></div>

<h3>Job Description</h3><div>Job Description<div><p><strong>AI Software Engineer</strong><b> Location: Plano, TX (Hybrid – onsite required)<b> Duration: 6+ Months Contract to Hire<b> Start Date: ASAP<b> <strong>Position Overview</strong><b> We are seeking an experienced AI Software Engineer to join a growing engineering team focused on building scalable AI-driven applications and data platforms. This is a hands-on technical role involving backend development, API engineering, cloud architecture, streaming data, and GenAI integrations.<b> The ideal candidate will work closely with technical leads and product owners to understand requirements, contribute to system design, develop scalable solutions, and support best engineering practices in a collaborative Agile environment.<b> <strong>Responsibilities</strong></b></b></b></b></b></b></b></p><ul><li>Design, develop, and maintain scalable backend applications and APIs </li><li>Build RESTful APIs using FastAPI and GraphQL APIs using Strawberry </li><li>Develop real-time data pipelines using Kafka or Event Hubs </li><li>Work with PostgreSQL, MongoDB, and distributed data systems </li><li>Implement scalable data processing workflows using Spark and Delta Lake </li><li>Utilize Databricks for data engineering and ML workflows </li><li>Integrate LLM APIs such as OpenAI, Llama, or other GenAI platforms </li><li>Deploy and manage applications using Docker and Kubernetes </li><li>Build and maintain CI/CD pipelines using Azure DevOps or GitHub Actions </li><li>Collaborate with cross-functional teams on architecture, design, and implementation </li><li>Troubleshoot performance issues and optimize application scalability </li></ul><strong>Required Skills</strong><ul><li>Strong experience with Python and modern web frameworks </li><li>Hands-on experience with FastAPI and GraphQL </li><li>Experience with Kafka or Event Hubs </li><li>Strong database experience with PostgreSQL and MongoDB </li><li>Experience with Spark, Delta Lake, and Databricks </li><li>Experience integrating OpenAI, Llama, or other LLM APIs </li><li>Strong understanding of Microsoft Azure cloud architecture </li><li>Experience with Docker and Kubernetes </li><li>Experience with CI/CD pipelines and DevOps practices </li><li>Strong system design and problem-solving skills </li><li>Experience handling concurrency, multithreading, or distributed systems </li></ul><strong>Preferred Skills</strong><ul><li>Experience with LangChain </li><li>Front-end experience with React, Next.js, or JavaScript </li><li>Telecom industry experience is a plus </li></ul><p><strong>Work Model</strong><b> Hybrid role based in Plano, TX. Candidates should be comfortable working onsite as required.</b></p><p>#M1<b> #DI-CB2</b></p><p></p><p>#L1 - KB1</p><p></p><b> <b>Ref: #404-IT Pittsburgh<p><b></b></p></b></b></div></div>

Calculate Moving Average	SQL	Easy
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A/B Test Significance	Statistics	Medium
Optimize Query Performance	SQL	Hard
Feature Importance Analysis	Machine Learning	Medium
Clean Missing Data	Python	Easy
Neural Network Architecture	Deep Learning	Hard
Calculate Cohort Retention	SQL	Medium
Bayesian Probability	Statistics	Easy
Recommend Similar Products	Machine Learning	Hard

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