PubMatic Software Engineer Interview Questions + Guide 2024

PubMatic is a leading independent technology company that optimizes digital advertising by delivering a cutting-edge, supply-side platform for the world’s foremost digital content creators. Since its inception in 2006, PubMatic’s robust infrastructure has facilitated real-time data processing, transforming it into a leader in scalable and innovative programmatic solutions.

This guide will walk you through PubMatic’s interview process, along with commonly asked PubMatic software engineer interview questions to help you prepare better. Whether conducted remotely or on-site, the interview experience is designed to evaluate your skills and ensure a smooth, engaging selection journey.

The interview process usually depends on the role and seniority, however, you can expect the following on a PubMatic software engineer interview:

Recruiter/Hiring Manager Call Screening

If your CV is shortlisted, a recruiter from Pubmatic’s Talent Acquisition Team will contact you to verify key details, such as your experience, skills, and availability. Behavioral questions may also be part of this initial screening.

The recruiter might also provide insights into the role and the company culture. This conversation typically lasts about 30 minutes and is your first opportunity to make a lasting impression.

Online Coding + MCQ Test

Pubmatic often conducts an initial online test comprising coding challenges and multiple-choice questions. This round usually lasts about an hour and is designed to assess your problem-solving skills and technical knowledge. Topics may include:

• Data Structures and Algorithms
• Java and C/C++
• Databases and SQL queries
• Operating Systems and Linux commands

Technical Virtual Interview

Successfully passing the online test leads to a more in-depth technical interview, typically conducted via video conference using platforms like BlueJeans. This stage includes live coding exercises and questions that test your understanding of various technical concepts.

Example questions might include:

• Remove a node from a linked list given only the node to be removed.
• Convert an array so that all even numbers precede all odd numbers in O(1) space.
• Design-related questions focused on low-level design (LLD).

Onsite/Virtual Technical Rounds

You may be invited to attend multiple technical rounds, which delve deeper into your coding abilities and problem-solving skills. These rounds can be conducted onsite or virtually and usually cover:

• Advanced coding problems
• Low-Level Design (LLD)
• System design
• Data Structures and Algorithms
• Operating Systems and Multithreading

Example questions could include:

• Reverse a linked list.
• Design a queue data structure from scratch.
• Discuss processes vs. threads.

Managerial Round

The managerial round focuses on behavioral questions and your ability to fit into the company’s culture. It serves as an opportunity for you to ask questions about Pubmatic and the role you’re applying for. This interview typically involves discussing your resume, past projects, and how you handle work-related challenges.

HR Interview

The final stage is the HR interview, which aims to assess your cultural fit within Pubmatic. This round usually lasts about 45 minutes and covers topics like your career goals, why you chose Pubmatic, and your salary expectations.

Typically, interviews at PubMatic vary by role and team, but commonly Software Engineer interviews follow a fairly standardized process across these question topics.

1. Write a program to determine the term frequency (TF) values for each term in a document.

Given a text document in the form of a string, write a program to determine the term frequency (TF) values for each term in the document. Round the term frequency to 2 decimal points.

2. Create a function get_ngrams to return a dictionary of n-grams and their frequency in a string.

Write a function get_ngrams to take in a word (string) and return a dictionary of n-grams and their frequency in the given string.

3. Write a function to return the sum of the elements in a matrix.

Given a matrix of integers, write a function that returns the sum of the elements in the matrix. The function should handle both positive and negative integers and return the sum as an integer.

4. Write a function to find the nearest common ancestor of two nodes in a binary tree.

Given a binary tree of unique positive numbers and two nodes as input, write a function to return the value of the nearest node that is a parent to both nodes. If one of the nodes doesn’t exist in the tree, return -1.

5. Write a function to add together all combinations of adjacent integers in a string.

Write a Python function that adds together all combinations of adjacent integers of a given string of integers named int_str.

6. How would you explain what a p-value is to someone who is not technical?

Explain the concept of a p-value in simple terms to a non-technical person, focusing on its role in determining the significance of results in experiments or studies.

7. What could be the cause of the decrease in overall capital approval rates?

Analyze why the overall capital approval rate dropped from 85% to 82% despite individual product approval rates staying flat or increasing. Consider factors like changes in the mix of products or external influences.

8. What is the probability that both flips result in the same side with one fair and one biased coin?

Calculate the probability that two flips of a randomly selected coin (one fair, one biased with ³⁄₄ heads) result in the same side.

9. What is the percentage chance a review is actually fake when the algorithm detects it as fake?

Given that 98% of reviews are legitimate and 2% are fake, and the algorithm’s accuracy rates, calculate the probability that a review is fake when identified as such by the algorithm.

10. What kind of analysis would you run for non-normal distribution in an AB test with low data at Uber Fleet?

Determine the appropriate analysis method for an AB test with non-normal distribution and low data volume at Uber Fleet, and explain how to measure which variant won.

11. What are the assumptions of linear regression?

List and explain the key assumptions that must be met for linear regression analysis to be valid.

12. How would you set up an A/B test for multiple changes in a sign-up funnel?

A team wants to A/B test changes like button color (red to blue) and position (top to bottom) to increase click-through rates. How would you design this test?

13. Where and how could you promote Instagram through Facebook?

You work on Facebook’s growth team and need to promote Instagram within the Facebook app. Where and how would you implement this promotion?

14. What metrics/graphs/models would you use to analyze churn behavior for different pricing plans?

Netflix has two pricing plans: $15/month and $100/year. An executive wants an analysis of churn behavior for these plans. What metrics, graphs, or models would you use to provide an overview of subscription performance?

15. How would you analyze an A/B test with non-normal distribution for Uber Fleet?

Uber Fleet has low data for experimentation, and an A/B test shows a non-normal distribution. What kind of analysis would you run, and how would you determine which variant won?

16. What retention rate is needed to surpass revenue from a non-subscription price?

You sell an e-commerce product for $29 with a 50% margin. You want to offer a monthly subscription at a 20% discount. What retention rate is required to surpass the revenue from the non-subscription price?

You should plan to brush up on any technical skills and try as many practice interview questions and mock interviews as possible. A few tips for acing your PubMatic Software Engineer interview include:

• Prepare for All Levels of Coding Questions: The technical interviews can range from basic to advanced levels. Be sure to practice coding questions extensively, focusing on data structures, algorithms, and problem-solving.
• Bring Your A-Game in Design Questions: Low-level design questions can be challenging if you’re not well-practiced. Brush up on system design principles and be ready to explain your thought process comprehensively.
• Showcase Your Behavioral Excellence: The HR and managerial rounds are crucial for demonstrating your soft skills and cultural fit. Be prepared to discuss your past experiences, challenges, and how you solved them.

What is the average salary for a Software Engineer at PubMatic?

According to Glassdoor, Software Engineers at PubMatic earn between $113K to $163K per year, with an average of $135K per year.

How long does the entire interview process take?

The timeline can vary depending on the candidate’s progress through each round and the company’s hiring schedule. Generally, the process may include an initial test, followed by 2-3 technical interviews, and a final HR round, making it a thorough evaluation.

What is the company culture at PubMatic like?

PubMatic boasts a collaborative and innovative work environment. Regular communication with HR and technical interviewers is highlighted as positive, and the company supports diversity and inclusion while offering various benefits such as stock options, healthcare, and flexible work schedules.

The interview process at PubMatic for the Software Engineer position is rigorous. Candidates can expect multiple technical rounds that feature coding challenges, data structures and algorithms, system design questions, and behavioral interviews.

To ace your interview at PubMatic, preparation is vital. Familiarize yourself with common interview questions that range from core Java, system design challenges, to data structures and algorithms. Dive deep into the company’s interview process and list of possible questions with our main PubMatic Interview Guide, which offers a comprehensive look at what to expect and how to prepare.

Good luck with your interview!