Ather

Role: Backend Engineer

College: Not Specified

Interview Date: June 2024

Interview Type: Full-Time

Result: Selected

Difficulty: Challenging but rewarding

Rounds: 4 rounds

Topics Asked: Data Structures, Algorithms, System Design, SQL, NoSQL, Microservices, Event-Driven Architecture, Kafka/RabbitMQ, Redis, Load Balancing, Fault Tolerance, Behavioral Questions

Experience:

The candidate interviewed for a Backend Engineer position at Ather Energy in June 2024 and received an offer. The process involved four rounds.

Round 1: Online Coding Test

This was a timed online assessment with algorithmic and backend-centric problems. It tested understanding of data structures, algorithms, and backend scenarios.

• Problem 1: Implement an API Rate Limiter. The task was to design a basic rate-limiting mechanism for an API, ensuring it could handle many requests while limiting clients to a predefined request limit. The candidate used a combination of sliding window algorithms and hash maps.
• Problem 2: Database Query Optimization. This involved optimizing a complex SQL query with 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.

Round 2: Technical Interview 1

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

• Design Question: Microservice for Handling Transactions. The candidate was asked to design a transaction handling system for a large-scale e-commerce platform, focusing on data consistency, fault tolerance, and scalability. The discussion included using an event-driven architecture with Kafka or RabbitMQ for data synchronization and Redis for caching frequently accessed data. Edge cases like sudden disconnections, incomplete ride data, and scooter battery failures were also explored, with the candidate proposing fallback mechanisms like local caching and periodic data syncing.
• Algorithm Problem: Find the Longest Path in a DAG (Directed Acyclic Graph).

Round 3: System Design Interview

This round was entirely focused on system design, challenging the candidate on scalability and fault tolerance. The candidate felt confident about their design choices.

Round 4: Behavioral and Cultural Fit Interview (HR Round)

The final round was an HR interview focusing on cultural fit and company values. Questions included "Why Ather Energy?", "Describe a Time You Handled a Technical Disagreement," and "How Do You Stay Updated with Backend Technologies?".

Tips for Future Candidates: Understand System Design (scalable systems, fault tolerance, data consistency), brush up on SQL and NoSQL, practice API and Microservices Design, and stay calm in behavioral interviews.