Browserstack Interview Experience | Backend Developer

Browserstack interview experience for freshers, BrowserStack machine coding round questions, browserstack backend interview experience
SDE Dev

Recently, I got an interview opportunity from BrowserStack for a backend role. The whole process had multiple rounds, starting from an HR call to coding rounds and a system design interview.

In this blog, I’ll share everything in detail—what they asked, how I prepared, and what I learned.


Round 1: HR Telephonic Call

I got a call from the HR at BrowserStack. She was friendly and started by asking some basic questions about my current situation and background. Here’s what she asked:

Questions:

  1. Why are you currently not working full-time?
    I explained my recent focus on learning, upskilling, and building side projects.

  2. What is your tech stack?
    I shared that I mainly work with Node.js, Express, MySQL, Redis, and sometimes use Socket.io for real-time features.

  3. Explain your recent project.
    I talked about my full-stack projects, especially those involving real-time updates and backend APIs.

  4. Salary Expectations?
    I gave a range based on market research and my skill level.

  5. What do you know about BrowserStack?
    I told her I knew BrowserStack helps developers test websites and apps across browsers and devices.

  6. Then she asked if I had hands-on experience with:

    • Unit testing

    • Socket.io

    • Computer Networks

    • Node.js

    • Express

    • MySQL

    • Redis

After this round, she sent me a link for the online assessment round.

Round 2: Online Assessment

⏱ Duration: 50 minutes



Format: 21 MCQs (Multiple Choice Questions)

The questions were from a wide range of topics:

  • HTML/CSS

  • JavaScript

  • Computer Networking

  • Operating Systems

Some questions were basic, while some required deep understanding of OS concepts like processes, file systems, and DNS.

Round 3: Machine Coding Round (Real-Time Log Viewer)

This was the most interesting and challenging round for me. It was a 2.5-hour coding test where I had to build a small real-time web application.

Problem Statement:

I was asked to build a log file watcher, like the tail -f command in UNIX. The log file was on the server, and my job was to show the latest updates on a web page without refreshing it.

 Requirements:

  1. Real-time updates:
    The webpage should show new log lines automatically using WebSockets.

  2. No refresh:
    Once the page loads, it should stay updated without reloading.

  3. Last 10 lines on load:
    When the user visits the page, show the last 10 lines from the log file.

  4. Large file support:
    The log file could be several GBs, so we had to optimize how we read it.

  5. No external tail libraries:
    We had to manually implement the logic to track file updates.

  6. Multiple clients:
    The solution had to support multiple users viewing the log file at the same time.

My Approach:

  • I used Node.js for the server and Socket.io to push updates to the client.

  • On the server side, I created a file stream that watched for new log entries.

  • For the frontend, I created a page at http://localhost/log that connects to the server via WebSocket and displays the logs in real-time.

  • To get the last 10 lines, I used a buffered reverse read approach to avoid reading the full file.

Questions After the Round:

After I submitted my code, the interviewer asked me some follow-up questions:

  • How did you approach this problem?

  • How would you make this solution scalable to 100x more users?

  • What buffer size did you use and why?

  • What edge cases did you handle?

  • How would you deploy and monitor this in production?

It was a deep technical discussion and helped me think more about performance and scalability.

Round 4: Director of Engineering (Tech + Resume Discussion)

This round was more focused on my experience and system design knowledge.

Topics Discussed:

  • My past projects and the roles I played in them.

  • Deep dive into system design concepts, especially related to real-time systems.

  • Questions about designing systems that scale.

  • A lot of the conversation was focused on thinking at scale and writing clean, testable, modular code.

Some Important Interview Questions They Asked:

Here are a few questions that I found challenging and interesting:

  1. If you have a 1 TB file and want to find the word "interview" inside it, how would you do that?
    (Hint: Efficient file reading, chunking, parallel processing.)

  2. How would you scale any of your projects to support millions of users?
    (Hint: Load balancing, caching, DB optimization, and horizontal scaling.)

  3. What happens when you open a website in the browser?
    (Hint: DNS lookup, TCP handshake, HTTP request, response rendering.)

  4. How do browsers and DNS work together?

These questions tested both my technical understanding and problem-solving skills.

Although I received positive feedback in both the machine coding and Director rounds, the overall decision was not in my favor. A few days later, I received a rejection email from BrowserStack.

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