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Yahoo Interview Questions

<p>Yahoo is one of the world's leading Internet media companies with products ranging from Email and News to Search and Sports</p>

Yahoo is one of the world's leading Internet media companies with products ranging from Email and News to Search and Sports

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Algorithms

Yahoo Interview Guides

<p>Let’s say we are given a table <code>user_logins</code>.</p>

<p>Using this table, calculate how many users logged in an identical number of times on January 1st, 2022.</p>

<p>For example, it may be the case that on that date three users logged in seven times, four users logged in five times, two users logged in ten times, etc.</p>

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

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

<p><code>user_logins</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>login_date</code></td>
<td>DATETIME</td>
</tr>
</tbody>
</table>
<p><strong>Output:</strong></p>

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

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

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


Find how many users logged in a certain number of times on a given day

Daily Logins

<p>You’re given a table called <code>annual_payments</code> for an annually billed B2B SAAS subscription product.</p>

<p><code>annual_payments</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>status</code></td>
<td>VARCHAR</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>amount</code></td>
<td>FLOAT</td>
</tr>

<tr>
<td><code>amount_refunded</code></td>
<td>FLOAT</td>
</tr>

<tr>
<td><code>product</code></td>
<td>VARCHAR</td>
</tr>

<tr>
<td><code>last_updated</code></td>
<td>DATETIME</td>
</tr>
</tbody>
</table>
<p>Users pay for the three different products: <code>&#39;PDF Editor&#39;</code>, <code>&#39;Cloud Storage&#39;</code>, and <code>&#39;Mobile CRM&#39;</code>.</p>

<p>How would you formulate a query to calculate the average annual retention, for each subsequent year, at the end of the year?</p>

<p>Retention rate is calculated as a percentage of active subscriptions at the end of the year \(T\) in the active subscriptions at the end of the previous year \((T-1)\).</p>

<p><strong>Example 1:</strong></p>

<p>User 1 bought a subscript to <code>PDF editor</code> in 2019 for the first time and renewed their subscription in 2020. In 2021, they canceled their subscription.
Retention rates should be calculated as:</p>

<table>
<thead>
<tr>
<th>2019</th>
<th>2020</th>
<th>2021</th>
</tr>
</thead>

<tbody>
<tr>
<td>0.00</td>
<td>1.00</td>
<td>0.00</td>
</tr>
</tbody>
</table>
<p><strong>Example 2:</strong></p>

<p>User 2 bought a subscription to <code>&#39;PDF Editor&#39;</code> in 2019 for the first time, renewed their subscription in 2020, and canceled a few days later in 2020.
Retention rates should be calculated as:</p>

<table>
<thead>
<tr>
<th>2019</th>
<th>2020</th>
<th>2021</th>
</tr>
</thead>

<tbody>
<tr>
<td>0.00</td>
<td>0.00</td>
<td>0.00</td>
</tr>
</tbody>
</table>
<p>Notes:</p>

<ol>
<li>The status column may contain the values <code>&#39;paid&#39;</code>, <code>&#39;refunded&#39;</code>, or <code>&#39;failed&#39;</code>.</li>
<li>A <code>&#39;failed&#39;</code> payment equates to a user canceling their subscription on the date the next payment is due.</li>
<li>If a user refunds a successful payment, then the row gets updated, and the status becomes <code>&#39;refunded&#39;</code>. The date of refund is recorded in <code>last_updated</code>.</li>
<li>When a refund occurs in year \(T\), the subscription is canceled. Users may purchase the same product again in the subsequent years, and it is considered a new purchase.</li>
</ol>


Annual Retention

<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>


Yahoo Interview Questions

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