I applied through an employee referral.

The Juspay interview process is a rigorous, multi-stage marathon known for its unique focus on deep technical problem-solving rather than standard competitive programming.

It begins with an online screening consisting of technical MCQs and a coding round featuring complex graph-based problems. Candidates who pass move to the Hackathon Part A, where they must solve the "Tree of Space" problem—an N-ary tree locking system—within a strict 3-hour window.

This is followed by the grueling Hackathon Part B, an 8+ hour marathon conducted via Slack where candidates must optimize their previous solution and make it thread-safe without using standard synchronization primitives like mutexes or semaphores. The process concludes with a series of technical interviews that dive deep into OS fundamentals, concurrency, and high-level system design.