Lenskart | SDE-2 (Backend) | Gurugram | Jan 2024 [Reject]

My Interview Experience at Lenskart

I applied for the SDE-2 Backend position at Lenskart through a referral. My previous role was Software Engineer II at Sabre, and I have 1.5 years of experience.

Telephonic Conversation with HR (5-10 mins)

The HR round was brief. I was asked about my current organization, CTC drawn, expected CTC, and tech stack. The HR also explained the overall interview process, which would consist of three technical rounds: DSA + CS Fundamentals, Heavy Coding (System Design), and Techno Managerial.

Technical Round 1: DSA + CS Fundamentals (1 hr)

This round started with a 20-minute project discussion. The interviewer, a tech lead with 8-9 years of experience, focused on my previous company's project, which utilized Java and Spring Boot. We discussed various aspects like the database schema, microservices architecture, and deployment strategies. My tip for others: be extremely thorough with your projects, understand the 'why' behind design choices, and be prepared to discuss potential improvements.

Problem Solving

Next, we moved to problem-solving. The first problem was similar to the GeeksforGeeks problem "Count pairs in array whose sum is divisible by k".

• Problem: You are given a list of songs where the ith song has a duration of time[i] seconds. Return the number of pairs of songs for which their total duration in seconds is multiple of 60.
• Example 1:

  Input: time = [30,20,150,100,40]
  Output: 3

• Example 2:

  Input: time = [60,60,60]
  Output: 3

I initially presented a brute-force O(n^2) solution. The interviewer then challenged me to optimize it further. I attempted a hash map approach, but it turned out to be incorrect, and I couldn't come up with a better optimization.

We then moved to the next question:

• Problem: Implement the operations add() and isPresent() of a HashSet in O(1) time.

I tried implementing this using a hash function, aiming for O(1) time complexity. There were several counter-questions regarding the internal implementation of HashSet and HashMap, covering concepts like loading factor and collision resolution. I was able to explain all these concepts thoroughly.

The final question was based on SQL:

• Problem: In an Employee table, employees belong to three different locations - Bengaluru, Delhi and Chennai. We need to return the count of all the employees belonging to these cities.

I provided a query using the GROUP BY clause, which satisfied the interviewer.

At the end, the interviewer asked if I had any questions before we concluded the call. My overall experience with the interviewer was positive, as they were supportive throughout. However, I knew my inability to optimize the first problem-solving question fully might hinder my progress.

Verdict

I received the rejection mail from HR about half an hour after the interview.