Juspay SDE Off-Campus 2025: 6 Rounds, Tree of Space, 9-Hour Hackathon B, Selected

TL;DR. Shreyansh Raj, BTech CSE, off-campus. Six rounds: MCQ assessment with a 67% cutoff on PCM and CS fundamentals; 3 LeetCode Medium-Hard coding problems (solved 2 completely, partial on 3rd, still cleared); Hackathon A where Tree of Space was solved via BFS in 30 minutes with O(N) time and O(1) space; an elimination round combining classic puzzles (lighter egg, meeting probability) with coding (prefix sum, array power optimization); Hackathon B spanning 9 hours requiring O(log N) Tree of Space optimization with thread safety implemented without mutex or locks, plus DNS interrogation on A vs AAAA records; and a System Design + Culture round covering idempotency, SSL certificates, and network security. Result: selected. Source linked at the bottom.

This is the companion piece to the on-campus rejection story: Juspay SDE On-Campus 2025: Tree of Space, 8-Hour Hackathon, 27 LPA, Rejected. Same company, same signature problem, same year. One candidate cleared, one did not. The differences are instructive.

Who cleared this pipeline

The off-campus process at Juspay has more rounds than the on-campus process. On-campus candidates go through 4 rounds; off-campus candidates go through 6. The extra 2 rounds (MCQ assessment and the elimination round) function as additional filters to compensate for the absence of campus-level screening.

The 6-round off-campus structure

Total active assessment time: approximately 16 hours across 6 rounds. This is more than any FAANG loop (Amazon: ~5 hours, Google L4: ~6-8 hours, Uber SDE-2: ~6 hours). The only comparable process is the on-campus Juspay loop at 13 hours, and this off-campus version exceeds it.

Round 1: MCQ Assessment

Content: "basic PCM along with CS fundamentals." PCM here means Physics, Chemistry, Mathematics, covering basic aptitude and reasoning. The CS fundamentals section covers data structures, operating systems, databases, and networking at a surface level.

Cutoff: 67%. The cutoff is generous. This round filters for baseline competence, not excellence. If your CS fundamentals are solid (you can answer "what is deadlock" and "explain normalization to 3NF" without hesitation), this round is a free pass.

Shreyansh cleared. Exact score not disclosed.

Round 2: Coding Challenge (90 minutes, 3 problems)

Difficulty: LeetCode Medium to Hard.

Shreyansh solved 2 completely and partially solved the 3rd. The cutoff was 67%, meaning 2 complete solutions out of 3 was sufficient.

This is an important data point. Many candidates assume they need to solve all 3 problems to advance. They do not. Solving 2 cleanly (all test cases passing) is enough. Spending 60 minutes on a perfect solution to problem 3 at the cost of incomplete solutions on problems 1 and 2 is the wrong optimization. Solve the first 2 fast and correctly, then invest remaining time in the hard problem.

Round 3: Hackathon A, Tree of Space (3 hours)

The same problem that appears in every Juspay cycle: the N-ary tree locking system.

Shreyansh's approach:

• Algorithm: BFS-based traversal
• Time complexity: O(N)
• Space complexity: O(1) (beyond the tree structure itself)
• Completion time: approximately 30 minutes
• Test case clearance: all cases passed

30 minutes out of a 3-hour window. This is significant. It means Shreyansh had practiced Tree of Space before the hackathon. He knew the problem shape, had an implementation ready, and spent the remaining 2.5 hours verifying correctness and cleaning up code.

The candidate's own observation: Tree of Space is "pretty standard when it comes to Juspay." It is published on GeeksforGeeks, discussed on LeetCode forums, and documented in multiple blog posts. Walking into Juspay's hackathon without having practiced this problem is like walking into an Amazon interview without knowing what a Bar Raiser is. The information is public. Use it.

Round 4: Elimination Round (unique to off-campus)

This round does not exist in the on-campus process. It combines:

Puzzles (2 problems)

Puzzles at Juspay are not throwaway warm-ups. They test structured reasoning under observation. The lighter egg puzzle is a standard CS interview puzzle (binary search analogy). The meeting probability puzzle requires geometric probability (area of overlap on a unit square). If you have worked through 20-30 classic CS puzzles from books like "How Would You Move Mount Fuji" or the puzzle sections of GFG, you have the preparation.

Coding (2 problems)

Shreyansh described this as "one of my best rounds." The coding problems were medium difficulty, and the prefix sum approach for array power optimization is a standard technique that appears frequently in competitive programming.

Round 5: Hackathon B (9 hours)

This is the defining round of Juspay's off-campus process, equivalent to the 8-hour Round 3 in the on-campus process.

The task: Take your Tree of Space solution from Hackathon A and:

1. Optimize it from O(N) to O(log N) per operation
2. Make it thread-safe without using any mutex, semaphore, or standard synchronization primitive

The no-mutex constraint is the critical detail. Most engineers reach for synchronized (Java) or threading.Lock() (Python) when they need thread safety. Juspay explicitly forbids this. They want to see lock-free data structures, compare-and-swap (CAS) operations, or immutable data structure patterns. This tests whether the candidate understands concurrency at the hardware/memory-model level, not just the library level.

The platform: Slack-based. The 9-hour session is conducted via a Slack channel where mentors ask questions, request explanations, and probe specific design decisions throughout the day.

Additional topics covered during Hackathon B:

• DNS fundamentals: A records vs AAAA records, why Google and CloudFlare use different DNS server architectures
• The DNS questions are not random. Juspay builds payment infrastructure that depends on DNS resolution latency. Understanding DNS at a systems level (not just "DNS resolves domain names to IPs") is relevant to the role.

Shreyansh cleared this round.

Round 6: System Design + Culture

Technical topics:

• Idempotency: what it means in the context of payment systems, how to implement idempotent APIs, what happens when a payment request is retried
• SSL certificates: how TLS handshakes work, certificate chains, pinning, what happens when a certificate expires mid-transaction
• Network security validation: how to verify that a request came from an authorized source

Culture topics:

• Personal hobbies and interests (Juspay values curiosity and self-driven learning)
• How the candidate handles ambiguity
• What motivates the candidate to work at a fintech infrastructure company

Shreyansh described this as "a tough round." The idempotency and SSL questions are directly relevant to Juspay's core business (payment processing), and generic system design answers ("use Redis for caching") do not satisfy interviewers who build payment infrastructure daily.

On-campus vs off-campus: the same problem, different outcomes

The companion article covers a Batch 2025 on-campus candidate (Kamal Chandra) who was eliminated at the 8-hour hackathon stage of Juspay's process. Shreyansh, the off-campus candidate, cleared the equivalent 9-hour hackathon and was selected.

Key differences between the two candidates' experiences:

The off-campus process is harder by every metric: longer, more rounds, stricter constraints. Yet the off-campus candidate cleared. The implication: prior preparation with Tree of Space (evidenced by the 30-minute solve time) and comfort with lock-free concurrency patterns (evidenced by clearing the no-mutex constraint) were the differentiators. Both are learnable skills. Neither requires genius. They require deliberate practice.

How to actually prepare for Juspay's hackathon rounds

1. Tree of Space is non-negotiable. Implement it 5 times from scratch, using 3 different approaches. Time yourself. Your target: working solution in 30 minutes or less.

2. O(log N) optimization path. The standard O(N) approach traverses the full subtree for lock checks. The O(log N) approach uses augmented tree nodes with cached locked-descendant counts, updated lazily during lock/unlock operations. Study this optimization specifically.

3. Lock-free concurrency. Study Java's AtomicReference, compareAndSet, and the CAS loop pattern. Implement a lock-free stack and a lock-free queue from scratch. If you can build these two data structures without mutexes, you have the foundation for the Tree of Space thread-safety requirement.

4. DNS and networking fundamentals. Read the DNS sections of "Computer Networking: A Top-Down Approach" (Kurose & Ross), chapters on DNS resolution, caching, and record types. Know A, AAAA, CNAME, MX, and NS records. Know the difference between recursive and iterative DNS resolution.

5. Idempotency in payment systems. Read Stripe's engineering blog post on idempotency keys. Understand why payment APIs require idempotency, how idempotency keys work, and what happens during network partitions.

6. Stamina management for 9-hour sessions. Prepare physically: 8 hours of sleep the night before, a protein-heavy breakfast, water and snacks within reach. Plan for a cognitive dip around hour 5-6 and schedule a 10-minute break. The 9-hour window is a marathon, not a sprint.

Where this data comes from

Source: Shreyansh Raj's Juspay Off-Campus Interview Experience on Medium

Similar verified interviews

• Juspay SDE On-Campus 2025: Tree of Space, 8-Hour Hackathon, 27 LPA, Rejected (same company, same problem, different outcome)
• Goldman Sachs Engineering Analyst 2025: The 10.5-Hour Campus Marathon (another ultra-long interview process)
• Intuit SDE-1 Off-Campus 2025: 7-Stage Build Challenge Offer (another company with a multi-hour coding challenge)
• Zepto SDE-1 Bangalore 2025: Air Traffic Controller LLD to Rejection (startup LLD round comparison)
• Flipkart SDE-1 Girls Wanna Code: 13,000 Applicants to Offer (campus pipeline with different structure)

Where this comes from: we compile these trends from public preparation resources and what candidates report after their drives. Use it as a study guide, and confirm fees, dates, and cut-offs on the official portal for the cycle you are sitting.