Ather Energy

Role: Software Development Engineer (SDE)

College: Not Specified

Interview Date: January 2025 (Applied May 2024)

Interview Type: Full-Time

Result: Selected

Difficulty: Medium-Hard

Rounds: 4 rounds

Topics Asked: Data Structures (Arrays, Binary Trees, Queues), Algorithms (Array manipulation, Binary Tree traversal, String manipulation), System Design (Notification system, Ride-sharing system, Microservices architecture, Data storage, Caching, Scalability, Fault tolerance), Behavioral questions.

Experience:

The candidate interviewed for an SDE position at Ather Energy in January 2025, having applied through Ather Energy's careers page in May 2024. The overall process was described as engaging, with questions blending technical depth and practical problem-solving.

Round 1: Online Coding Test

This round consisted of two medium-difficulty coding questions.

• Question 1: Rearranging an array to have all even numbers on one side and all odd numbers on the other, including edge cases like negative numbers and zeros.
• Question 2: Binary tree traversal to print the level order traversal in a zigzag pattern, using a queue and reversing output for alternating levels.

The candidate passed all test cases and received an email for the next round three days later.

Round 2: Technical Interview 1

This round combined coding and basic system design, lasting about 60 minutes. The interviewer started by asking about the candidate's projects, specifically a machine learning model.

• Coding Problem: String manipulation to remove adjacent duplicates until no more could be removed. The interviewer was satisfied with the brute-force solution.
• System Design: Designing a notification system, focusing on handling real-time updates, scaling, and user preferences.

The candidate felt confident after this round and was scheduled for the next one two days later.

Round 3: Technical Interview 2 (System Design Focus)

This round was described as a "mental marathon," focusing on designing a ride-sharing system similar to Uber for electric scooters. The interviewer emphasized scalable and efficient system design.

• Design Task: Outline a microservices architecture for users, rides, and payments; data storage for live scooter locations; caching mechanisms for frequently accessed data; and scalability concerns for features like live tracking and dynamic pricing.

The candidate discussed handling scooter maintenance, downtimes, ride cancellations, and database choices (NoSQL for real-time location). They also addressed a potential bottleneck in their caching strategy by adjusting to distributed cache systems. Despite a moment of self-doubt, the candidate passed this round.

Round 4: HR Round

This round focused on behavioral questions and cultural fit. The conversation was friendly but insightful.

• Questions: Analyzing a hypothetical situation about balancing multiple priorities.

The candidate was initially convinced they wouldn't pass this round but received an offer a week later. They were later informed that the company valued their thought process over a "perfect" answer.