Preparing for an interview at Pubmatic requires a balanced approach to software engineering, system administration, and quality assurance principles. You must demonstrate that you can think like both a developer and a rigorous tester.

Coding and Logic – You must be ready to write clean, syntax-accurate code during your technical rounds. Interviewers heavily evaluate your choice of data structures, algorithmic efficiency, and ability to dry-run your code.

Database Proficiency – Expect to write SQL queries in almost every technical round. Focus on mastering joins, subqueries, and aggregation, as data validation is a core part of testing ad-tech pipelines.

System and Infrastructure Fundamentals – Brush up on core Linux commands and networking basics. Understanding how servers communicate and how to inspect log files is critical for backend QA roles.

Automation and Framework Design – Be prepared to explain how you structure test automation suites. Focus on scalability, maintainability, and how you integrate tests into a continuous integration pipeline.

The interview process at Pubmatic is comprehensive and technically rigorous, designed to thoroughly evaluate your hands-on engineering capabilities. The entire process typically spans two to four weeks, though the timeline can vary depending on the location and hiring team.

The journey begins with an initial screening. In some regions, particularly for campus or pool drives, this starts with a pen-and-paper or online test covering aptitude, technical concepts, programming, and SQL. Be aware that these initial tests may feature negative marking, requiring you to be precise and deliberate with your answers. Alternatively, you may receive a HackerRank coding challenge featuring multiple programming and algorithmic tasks.

Following the initial screen, you will progress through multiple technical rounds. Pubmatic is known for a thorough technical evaluation, which often consists of three to four rounds. These sessions are highly focused on live coding, SQL query design, Linux command-line exercises, and automation framework architecture. You will wrap up with a techno-managerial round and an HR discussion to evaluate team collaboration and alignment with company culture.

The visual timeline above outlines the typical progression from your initial technical screening through to the final offer stage. Candidates should use this sequence to pace their preparation, ensuring they master foundational coding and SQL skills before moving on to complex system and framework discussions.

To succeed at Pubmatic, you must understand the specific competencies your interviewers will be evaluating. Each round is structured to test a distinct layer of your technical toolkit.

Coding and Problem Solving

Pubmatic operates a 100% automation environment, meaning every QA Engineer must write production-quality code. This area evaluates your ability to translate logical solutions into functional code.

Be ready to go over:

• Core Java or Python – Proficiency in language fundamentals, including OOP concepts and memory management.
• Collections Framework – Efficient use of lists, sets, maps, and queues to manipulate data.
• String and Array Manipulation – Common algorithms for searching, sorting, and restructuring data.
• Advanced concepts – Basic data structures like stacks and queues, as well as light dynamic programming concepts for optimization.

Example questions or scenarios:

• "Write a program to find the first non-repeating character in a string using a single pass."
• "Implement a function that checks if brackets in an expression are balanced using a stack."

SQL and Database Systems

Ad-tech platforms generate massive amounts of transactional data. You must prove that you can query, validate, and troubleshoot database records efficiently.

Be ready to go over:

• Relational Database Concepts – Understanding schemas, primary/foreign keys, and normalization.
• Advanced Querying – Writing nested subqueries, using analytical functions, and grouping datasets.
• Data Validation – Verifying backend database state against expected frontend or API outputs.
• Advanced concepts – Database indexing, performance tuning, and analyzing slow-running queries.

Example questions or scenarios:

• "Given an Employee table, write a query to find the third-highest salary without using the LIMIT keyword."
• "Write a SQL query using a LEFT JOIN to identify publishers who have not generated any ad impressions in the last 24 hours."

Linux, Networking, and Remote Systems

Since Pubmatic's application stack runs on high-performance servers, you must demonstrate the ability to navigate these environments to diagnose issues.

Be ready to go over:

• Command-Line Navigation – Moving through directories, managing file permissions, and viewing file contents.
• Log Parsing – Utilizing text-processing tools to isolate errors in massive log files.
• Networking Basics – Understanding client-server communication, DNS, and ports.
• Advanced concepts – Remote connectivity protocols, analyzing network latency, and interpreting complex system resource metrics.

Example questions or scenarios:

• "How would you find and count the occurrences of a '404' error in an access log file using Linux commands?"
• "Explain the steps you would take to troubleshoot a connection timeout issue between an ad server and a database."

Test Automation and Ad-Tech Scenarios

This area tests your ability to design scalable test suites and apply QA methodologies to complex business requirements.

Be ready to go over:

• Automation Frameworks – Designing and maintaining frameworks using tools like Selenium, TestNG, or PyTest.
• API Testing – Validating RESTful endpoints, request/response payloads, and response times.
• Ad-Tech Domain Testing – Understanding how to test real-time bidding, ad delivery, and cookie syncing.
• Advanced concepts – Parallel execution, CI/CD pipeline integration, and performance/load testing of high-throughput APIs.

Example questions or scenarios:

• "How would you design a test automation suite to validate that an ad-serving API correctly applies targeting criteria (e.g., geo-location, device type) to incoming requests?"
• "Explain how you would handle dynamic, slow-loading elements in a web application without using hardcoded sleep statements."