Ather Energy

Role: Backend Engineer

College: Not Specified

Interview Date: June 2024

Interview Type: Full-Time

Result: Selected

Difficulty: Medium-Hard

Rounds: 3 rounds

Topics Asked: Data Structures, Algorithms, Backend-centric problems, API Rate Limiting, Database Query Optimization, Microservices Architecture, Transaction Handling Systems, Database Design (NoSQL, Relational), Caching (Redis), Load Balancing, Fault Tolerance, Behavioral questions.

Experience:

The candidate interviewed for a Backend Engineer position at Ather Energy in June 2024. The job was discovered via GetJobs.Today. The overall interview process was described as challenging but rewarding, covering technical depth, problem-solving, and real-world system design.

Round 1: Online Coding Test

This was a timed online assessment with algorithmic and backend-centric problems testing data structures, algorithms, and backend scenarios.

• Problem 1: Implement an API Rate Limiter: Design a basic rate-limiting mechanism to handle a large number of requests while ensuring clients don't exceed a predefined limit. The candidate used a combination of sliding window algorithms and hash maps.
• Problem 2: Database Query Optimization: Optimize a complex SQL query involving multiple joins and aggregations on large datasets, testing knowledge of database indexing, query optimization, and SQL performance tuning.

The candidate solved both problems within the time limit and passed all test cases. Approximately 70 out of 300 candidates advanced to the next round.

Round 2: Technical Interview 1

This round focused on backend systems and core algorithms. The interviewer inquired about the candidate's previous experience, particularly a microservices architecture project.

• Design Question: Microservice for Handling Transactions: Design a transaction handling system for a large-scale application. The discussion covered microservices architecture, API design, data consistency, and error handling. For scooter tracking, the candidate opted for a NoSQL database like MongoDB for real-time location data, and a relational database for user management and payments to ensure ACID compliance.
• Caching & Load Balancing: Discussion included implementing Redis as a caching layer for frequently accessed data (scooter availability, user preferences) and load balancing for high traffic.
• Edge Cases: The interviewer challenged the candidate to consider failure scenarios like disconnections, incomplete ride data, and battery failures.

This round was intense but rewarding, and the candidate felt confident about their design choices.

Round 3: HR Interview

The final round was an HR interview focused on cultural fit.

• Questions: "Why Ather Energy?" (Candidate discussed interest in EVs and Ather's innovation, and how their skills could scale products). "Describe a Time You Handled a Technical Disagreement:" (Candidate shared an experience of team disagreement on database technology and how a collaborative decision was reached). "How Do You Stay Updated with Backend Technologies?" (Candidate mentioned following tech blogs, webinars, and coding challenges).

A week after the final round, the candidate received an offer from Ather Energy.