Role Information

• Position: Senior Developer (UI)
• Application Date: September 2025
• Application Method: Referral
• Total Rounds: 5

Round 1: JavaScript Fundamentals

Duration: 60 minutes

Questions Asked:

1. Closures

   • Explain what closures are
   • Provide code examples

2. Debounce and Throttle

   • Implement debounce and throttle in vanilla JavaScript

3. Promises

   • Explain what promises are
   • Write a polyfill for Promise.all()

4. Promise Chain Output

   Promise.resolve(1)
     .then((val) => {
       console.log(val);
       return val + 1;
     })
     .then((val) => {
       console.log(val);
     })
     .then((val) => {
       console.log(val);
       return Promise.resolve(3).then((val) => {
         console.log(val);
       });
     })
     .then((val) => {
       console.log(val);
       return Promise.reject(4);
     })
     .catch((val) => {
       console.log(val);
     })
     .finally((val) => {
       console.log(val);
       return 10;
     })
     .then((val) => {
       console.log(val);
     });

5. 'this' Keyword Behavior

   const obj = {
     dev: "bfe",
     a: function () {
       return this.dev;
     },
     b() {
       return this.dev;
     },
     c: () => {
       return this.dev;
     },
     d: function () {
       return (() => {
         return this.dev;
       })();
     },
     e: function () {
       return this.b();
     },
     f: function () {
       return this.b;
     },
     g: function () {
       return this.c();
     },
     h: function () {
       return this.c;
     },
     i: function () {
       return () => {
         return this.dev;
       };
     },
   };
   
   console.log(obj.a());
   console.log(obj.b());
   console.log(obj.c());
   console.log(obj.d());
   console.log(obj.e());
   console.log(obj.f()());
   console.log(obj.g());
   console.log(obj.h()());
   console.log(obj.i()());

6. Event Loop and Microtasks

   console.log(1);
   const promise = new Promise((resolve) => {
     console.log(2);
     resolve();
     console.log(3);
   });
   
   console.log(4);
   
   promise
     .then(() => {
       console.log(5);
     })
     .then(() => {
       console.log(6);
     });
   
   console.log(7);
   
   setTimeout(() => {
     console.log(8);
   }, 10);
   
   setTimeout(() => {
     console.log(9);
   }, 0);

7. var vs let in Loops

   for (var i = 0; i < 5; i++) {
     setTimeout(() => console.log(i), 0);
   }
   
   for (let i = 0; i < 5; i++) {
     setTimeout(() => console.log(i), 0);
   }

8. Hoisting and Variable Scope

   var a = 1;
   
   function func() {
     a = 2;
     console.log(a);
     var a;
   }
   
   func();
   
   console.log(a);
   
   if (!("b" in window)) {
     var b = 1;
   }
   
   console.log(b);

9. Array.prototype.reduce Polyfill

   • Write a polyfill for the reduce method

Round 2: Machine Coding

Duration: 60 minutes

Main Task:

Build a To-Do List Application with the following requirements:

• Three filter tabs: Completed, In Progress, and Deleted
• Display tasks based on the selected filter
• Handle keyboard interactions (e.g., add new task on Enter key press)

Additional Question (after early completion):

Promise.resolve(1)
  .then(() => 2)
  .then(3)
  .then((value) => value * 3)
  .then(Promise.resolve(4))
  .then(console.log);

Round 3: System Design

Duration: 60 minutes
Interviewer: Lead Engineer

Topics Covered:

1. Project Discussion

   • Detailed discussion about past projects

2. Optimization Techniques

   • Virtualization
   • Lazy loading
   • Write pseudo-code to implement virtualization with vanilla JavaScript using Intersection Observer

3. React Performance

   • React Profiler and its usage for performance optimization

4. Architecture

   • Micro-frontend architecture (theory knowledge)

Round 4: Hiring Manager

Duration: 60 minutes
Interviewer: Engineering Manager

Topics Covered:

1. Career Discussion

   • Career journey and background

2. System Design

   • Message queues (despite UI-focused profile)
   • Role-based authentication application implementation
   • How to show pages based on user roles

3. Behavioral Assessment

   • Situational questions
   • Cultural fit questions

Round 5: Final Tech Round

Duration: 60 minutes

Note: Before this round, the recruiter informed that all rounds were cleared with positive feedback. Offer letter rollout was expected by Monday. However, on Monday, they scheduled one more round on design and coding.

Topics Covered:

1. Introduction and Project Discussion

   • Explained migration from Gatsby to React at Fairmatic
   • Follow-up questions on design choices
   • Collaboration with Manager, Junior Developers, and Product Managers

2. React Coding Challenge

   • Question based on async behavior
   • Misunderstood the question and coded a complex solution (which was working)
   • Interviewer asked for a simpler solution, which I could not implement during the interviewer

Outcome:

• Feedback: "Do Not Proceed"
• Result: Rejected

Overall Experience

The overall experience after 4 rounds were okayish. But 5th round was not good as per feedback. I got "Do Not Proceed" feedback in 5th round due to which I got rejected. The 5th round interviewer gave a very bad feedback actually which I was very surprised because I gave a complex solution for a simple solution. This made me sad and I was frustrated because I was told that Hiring Manager liked me and they will roll out offer letter soon and then in 5th round which was not excellent I was rejected. I had to go through 5 rounds because it was for the main platform team there, I have heard other people had max 3 rounds.