Moloco Software Engineer Interview Questions + Guide in 2025

Moloco is a machine learning company dedicated to empowering organizations of all sizes to harness the full potential of their first-party data for performance advertising.

As a Software Engineer at Moloco, you will play a pivotal role in designing, developing, and maintaining backend systems for their advanced Moloco Commerce Media (MCM) product. Key responsibilities include creating server APIs and web services, writing server-side code capable of handling millions of requests per second, and building robust cloud infrastructure. You will also be tasked with transforming unstructured logs and events into structured data for analytics and machine learning, while designing efficient data pipelines to manage big data. In addition to these technical challenges, you will collaborate closely with other software and machine learning engineers to enhance the security and functionality of systems, as well as ideate new features for future advertising solutions.

To excel in this role, you should have a minimum of 6 years of software development experience focusing on backend and infrastructure systems, alongside a Bachelor's degree in Computer Science or a related field. Proficiency in programming languages such as Golang, Java, or Python is essential, along with experience in large-scale distributed systems and cloud platforms (AWS, GCP, etc.). Strong problem-solving skills, system design capabilities, and a strategic mindset are critical traits for success, particularly when navigating the complexities of ad services and performance optimization.

This guide will help you prepare effectively for your interview by outlining the key areas to focus on that align with Moloco's mission and core values, ultimately enhancing your chances of success.

The interview process for a Software Engineer at Moloco is structured to assess both technical and interpersonal skills, ensuring candidates align with the company's values and technical requirements. The process typically consists of several key stages:

1. Initial Screening

The first step involves a phone call with a recruiter, which usually lasts about 30 minutes. During this conversation, the recruiter will discuss the role, the company culture, and your background. This is an opportunity for you to express your interest in the position and ask any preliminary questions about the company and its projects.

2. Technical Assessment

Following the initial screening, candidates are often required to complete an online coding assessment. This assessment typically includes a mix of algorithmic problems, SQL queries, and questions related to statistics and machine learning concepts. The assessment is designed to evaluate your coding skills and understanding of fundamental software engineering principles.

3. Technical Interviews

Candidates who perform well in the assessment will be invited to participate in multiple technical interviews. These interviews usually consist of three rounds, each lasting about 45 minutes to an hour. Interviewers may include senior engineers and team leads. The focus will be on problem-solving, coding challenges, and system design. Expect questions that test your knowledge of distributed systems, cloud infrastructure, and backend development practices. You may also be asked to explain your past projects and how they relate to the role.

4. Behavioral Interview

In addition to technical skills, Moloco places a strong emphasis on cultural fit. A behavioral interview is typically conducted to assess your alignment with the company's values, such as collaboration, humility, and a growth mindset. Be prepared to discuss your experiences working in teams, handling challenges, and how you approach learning and development.

5. Final Interview with Hiring Manager

The final stage usually involves a conversation with the hiring manager. This interview may cover both technical and behavioral aspects, focusing on your potential contributions to the team and the company. The hiring manager will likely explore your long-term career goals and how they align with Moloco's mission and vision.

Throughout the process, candidates can expect prompt feedback and communication from the recruitment team, reflecting Moloco's commitment to a respectful and efficient hiring experience.

As you prepare for your interviews, consider the types of questions that may arise in each stage, particularly those that assess your technical expertise and cultural fit.

Here are some tips to help you excel in your interview.

Understand the Technical Landscape

Given Moloco's focus on machine learning and backend infrastructure, it's crucial to familiarize yourself with the technologies and frameworks they use. Brush up on your knowledge of cloud platforms like AWS and GCP, as well as programming languages such as Golang, Java, and Python. Be prepared to discuss your experience with large-scale distributed systems and how you've tackled challenges in this area.

Prepare for a Mix of Questions

Interviews at Moloco often include a blend of technical and behavioral questions. Expect to demonstrate your problem-solving skills through coding challenges and system design questions. Additionally, be ready to discuss your past projects in detail, particularly those that involved backend development, data pipelines, or machine learning applications. This will showcase your ability to contribute to their Commerce Media product.

Emphasize Collaboration and Leadership

Moloco values teamwork and collaboration, so be prepared to discuss how you've worked with cross-functional teams in the past. Highlight any experience you have in mentoring or leading other engineers, as this aligns with their emphasis on fostering a collaborative environment. Share specific examples of how you've contributed to team success and how you handle feedback and accountability.

Showcase Your Growth Mindset

Moloco's culture encourages continuous learning and improvement. Be ready to discuss how you've approached challenges as opportunities for growth. Share instances where you've taken intelligent risks or experimented with new technologies, and how those experiences have shaped your professional development.

Align with Company Values

Familiarize yourself with Moloco's core values, such as leading with humility and creating real value. During the interview, reflect these values in your responses. For example, when discussing past experiences, emphasize how you valued team input, learned from failures, and focused on delivering impactful results.

Prepare for a Structured Interview Process

Candidates have noted that the interview process at Moloco can be well-organized but may also include unexpected elements, such as interviewers being unprepared. Stay adaptable and maintain a positive attitude throughout the process. If you encounter a situation where the interview doesn't go as planned, focus on demonstrating your technical skills and problem-solving abilities.

Follow Up Thoughtfully

After your interview, consider sending a follow-up email to express your gratitude for the opportunity and reiterate your interest in the role. This not only shows professionalism but also aligns with Moloco's value of collaboration and respect for others.

By preparing thoroughly and aligning your approach with Moloco's culture and values, you'll position yourself as a strong candidate for the software engineer role. Good luck!

In this section, we’ll review the various interview questions that might be asked during a software engineering interview at Moloco. Candidates should focus on demonstrating their technical expertise, problem-solving abilities, and experience with large-scale systems, as well as their understanding of machine learning and backend development.

Technical Skills

1. Can you explain the difference between a stack and a queue?

Understanding data structures is fundamental for backend development.

How to Answer

Discuss the characteristics of both data structures, including their operations and use cases.

Example

“A stack is a Last In First Out (LIFO) structure, where the last element added is the first to be removed. A queue, on the other hand, is a First In First Out (FIFO) structure, where the first element added is the first to be removed. Stacks are often used in function call management, while queues are used in scheduling tasks.”

2. How would you optimize a slow SQL query?

Performance optimization is crucial in handling large datasets.

How to Answer

Mention techniques such as indexing, query restructuring, and analyzing execution plans.

Example

“I would start by analyzing the execution plan to identify bottlenecks. If the query is scanning large tables, I would consider adding indexes on the columns used in WHERE clauses. Additionally, I would look for opportunities to rewrite the query to reduce complexity and improve performance.”

3. Describe a time you had to debug a complex issue in a production environment.

Debugging skills are essential for maintaining system reliability.

How to Answer

Share a specific example, focusing on your approach to identifying and resolving the issue.

Example

“In a previous role, we experienced a sudden spike in error rates. I used logging to trace the issue back to a recent deployment. By rolling back the changes and analyzing the code, I identified a race condition that was causing the errors. I implemented a fix and monitored the system to ensure stability.”

4. What is your experience with cloud platforms, and how have you utilized them in your projects?

Cloud infrastructure is a key component of Moloco's operations.

How to Answer

Discuss specific cloud services you’ve used and how they contributed to your projects.

Example

“I have extensive experience with AWS, particularly with EC2 for scalable computing and S3 for storage. In my last project, I used AWS Lambda to create serverless functions that processed data in real-time, which significantly reduced costs and improved scalability.”

5. How do you ensure the security of your applications?

Security is a priority in software development.

How to Answer

Mention best practices such as input validation, authentication, and regular security audits.

Example

“I ensure security by implementing input validation to prevent injection attacks, using secure authentication methods like OAuth, and regularly conducting security audits. Additionally, I keep dependencies updated to mitigate vulnerabilities.”

Machine Learning and Data Handling

1. Explain the concept of overfitting in machine learning.

Understanding machine learning principles is important for the role.

How to Answer

Define overfitting and discuss its implications on model performance.

Example

“Overfitting occurs when a model learns the training data too well, capturing noise instead of the underlying pattern. This results in poor performance on unseen data. To mitigate overfitting, I use techniques like cross-validation, regularization, and pruning.”

2. How would you design a fraud detection system?

This question assesses your ability to apply machine learning in practical scenarios.

How to Answer

Outline the steps involved in designing such a system, including data collection, feature engineering, and model selection.

Example

“I would start by collecting historical transaction data, then perform feature engineering to identify patterns indicative of fraud. I would use a combination of supervised learning for known fraud cases and unsupervised learning for anomaly detection. Finally, I would continuously monitor the model’s performance and retrain it with new data.”

3. What is a p-value, and why is it important?

Statistical knowledge is essential for data-driven decision-making.

How to Answer

Define p-value and explain its significance in hypothesis testing.

Example

“A p-value measures the probability of obtaining results at least as extreme as the observed results, assuming the null hypothesis is true. It helps determine the statistical significance of results, guiding decisions on whether to reject the null hypothesis.”

4. Can you explain Simpson's Paradox?

This question tests your understanding of statistical concepts.

How to Answer

Describe the paradox and provide an example to illustrate it.

Example

“Simpson's Paradox occurs when a trend appears in several different groups of data but disappears or reverses when these groups are combined. For instance, if two treatments are compared, one may appear better in both groups, but when combined, the overall results may show the opposite trend due to confounding variables.”

5. How do you handle missing data in a dataset?

Data preprocessing is a critical step in machine learning.

How to Answer

Discuss various strategies for dealing with missing data, such as imputation or removal.

Example

“I handle missing data by first assessing the extent and pattern of the missingness. Depending on the situation, I might use imputation techniques like mean or median substitution, or I may choose to remove records with excessive missing values if they could skew the analysis.”

System Design and Architecture

1. How would you design a system that can handle millions of requests per second?

This question evaluates your system design skills.

How to Answer

Discuss architectural patterns, load balancing, and database sharding.

Example

“I would design a microservices architecture to ensure scalability and maintainability. I would implement load balancers to distribute traffic evenly across instances and use database sharding to manage large datasets efficiently. Additionally, I would leverage caching mechanisms to reduce database load.”

2. Describe your experience with API design.

APIs are crucial for backend development.

How to Answer

Share your approach to designing RESTful APIs, including best practices.

Example

“I focus on creating RESTful APIs that are intuitive and follow standard conventions. I ensure proper use of HTTP methods, meaningful endpoint names, and clear documentation. Additionally, I implement versioning to maintain backward compatibility.”

3. What strategies do you use for testing and deploying code?

Testing and deployment are vital for software quality.

How to Answer

Discuss your experience with CI/CD pipelines and testing frameworks.

Example

“I utilize CI/CD pipelines to automate testing and deployment processes. I write unit and integration tests to ensure code quality and use tools like Jenkins or GitHub Actions for continuous integration. This approach allows for rapid deployment while maintaining high standards.”

4. How do you approach system monitoring and performance tuning?

Monitoring is essential for maintaining system health.

How to Answer

Explain your methods for monitoring system performance and making adjustments.

Example

“I use monitoring tools like Prometheus and Grafana to track system performance metrics. I analyze these metrics to identify bottlenecks and make necessary adjustments, such as optimizing queries or scaling resources, to ensure optimal performance.”

5. Can you discuss a project where you had to lead a team?

Leadership skills are important for collaboration.

How to Answer

Share your experience in leading a project, focusing on your role and the outcome.

Example

“I led a team of five engineers in developing a new feature for our product. I facilitated regular stand-ups to ensure alignment and encouraged open communication. By fostering a collaborative environment, we successfully delivered the feature ahead of schedule, which improved user engagement by 20%.”