Juspay is a Bengaluru payments technology company whose platform sits between merchants, payment gateways and banks. Among Indian engineers it is known for an unusual choice: much of its stack is written in the functional languages Haskell and PureScript. Candidates report graph-heavy online tests, long problem-solving rounds with concurrency follow-ups, and hackathon-style rounds in which they learn as they build. This page covers what Juspay builds and who it hires, the process candidates commonly report, the technical depth the teams care about, representative problem types, what interviewers score, and a three-week prep plan.
What Juspay builds and who it hires
Juspay's engineers build payment orchestration for large merchants, checkout and UPI SDKs that run inside merchants' apps, and the reliability systems that keep payments flowing when a gateway degrades. Its website listed more than 400 million transactions a day, over $1 trillion in annual payment volume and peaks above 50,000 transactions per second when checked on November 12, 2026. Juspay's careers pages describe heavy investment in functional programming with Haskell and PureScript, its engineers have cited about a million lines of Haskell in public talks, and its open-source payments switch, Hyperswitch, is written in Rust.
- SDE (freshers): hired largely through campus drives and the Juspay Hiring Challenge, often as a long, full-time internship before a full-time offer.
- SDE, functional programming: back-end services in Haskell.
- SDE, UI frameworks: the Hyper SDK and checkout front ends in JavaScript and PureScript.
- Rust and open-source engineers: Hyperswitch.
What the process tends to look like
| Stage | What happens | How to prepare |
|---|---|---|
| Application, campus drive or Hiring Challenge | Eligibility, role (SDE, UI or functional programming) and timeline | Read Juspay's product pages and know your résumé in detail |
| Online assessment | Reports describe three DSA problems in about 90 minutes, mostly on graphs, sometimes after an MCQ round on DSA, OS, networks and aptitude | Cycles, reachability and shortest paths on directed graphs |
| Problem solving, part A | One problem over about 90 minutes, such as locking and unlocking nodes in a tree, with complexity analysis | Tree operations with ancestor and descendant checks |
| Problem solving, part B | The same problem extended: thread safety, in some reports without standard locks, and rollback on failure | Race conditions, atomic compare-and-swap and undoing partial updates |
| Hackathon or learnathon | A long build, reported at three to nine hours, sometimes in an unfamiliar language such as PureScript | Learn functional basics and practice building under time pressure |
| Onsite and culture fit | Reports vary: system design, a day of reasoning problems outside software, or a culture conversation | Explain your reasoning aloud and stay curious |
Processes differ by team, level and office and change over time, so treat this as the common shape candidates report and confirm the specifics with your recruiter.
Functional programming, concurrency and payments
The functional-programming angle. Candidate reports suggest Juspay does not expect most applicants to know Haskell or PureScript beforehand. What they describe is a hackathon or learnathon in which they pick up PureScript and build something, such as a cube-rotation exercise reported across several years. A few hours with a Haskell or PureScript tutorial, practicing pure functions, immutable data, recursion, map, filter and fold, makes that day far less stressful.
Concurrency follow-ups. A widely reported problem asks you to lock, unlock and upgrade nodes in an m-ary tree under ancestor and descendant rules, then make the operations safe when many threads call them at once. Know how to reason about race conditions, atomic compare-and-swap and rolling back a partial update, and be ready to defend your complexity.
Payments reliability. Juspay's business is routing each payment to the gateway most likely to succeed and recovering when one degrades. Prepare to discuss success-rate-based routing, retries that never charge twice, idempotency and reconciliation. A 2024 Hyperswitch engineering post also describes replaying production payloads in a test environment and rolling out releases from 1 percent of traffic upward.
Representative problem types
These are the kinds of problems candidates describe, not a leaked question list. Practice the category, not the exact question.
- Graph problems on a maze where each cell has at most one exit: the largest cycle, the busiest node, the nearest meeting cell.
- Lock, unlock and upgrade nodes in an m-ary tree under ancestor and descendant rules.
- Make a tree-locking API thread-safe with atomic operations and rollback.
- Design payment routing that picks the gateway with the best recent success rate.
- Design an idempotent payment status flow with webhooks and reconciliation.
- Write small pure functions with map, filter and fold in a functional language.
- Multithreading questions on race conditions and deadlocks.
What interviewers score
- Working code: a solution that runs, handles edge cases and is readable by the next engineer.
- Practical judgment: the trade-offs you name and the simplest design that meets the requirement.
- Product sense: understanding who the user is and what failure looks like for them.
- Ownership: examples where you shipped, measured and fixed things yourself.
The behavioral side
Technical rounds decide most outcomes, but every Juspay loop also asks about how you work. Prepare a short story for each of these, with a result and what you learned:
- Something you shipped end to end. Cover the user problem, your decisions, what you measured and what you would change.
- A disagreement with a teammate. Show how you made the decision on evidence and kept the relationship.
- Why this company? Connect its product and engineering problems to the work you want to do next.
Structures and sample answers for the common questions are in our software engineer behavioral answers guide.
A three-week prep plan
- Week 1: practical coding: build small features against an API, parse and transform data, and write tests, in the language you will interview in.
- Week 2: system design for the company's domain, plus two behavioral stories about shipping and fixing something under pressure.
- Week 3: timed mixed problems, a mock interview every other day, and research into the product and its engineering blog.
For practice lists, use LeetCode company-tagged questions, the Striver A2Z sheet or the Love Babbar 450 sheet, and if your drive starts with a test, read our guide to new-grad online assessments.
Where CoPilot Interview fits
Most of a Juspay loop is spoken: you explain an approach, defend a trade-off and talk through your past work. CoPilot Interview is an AI interview assistant whose free AI mock interview builds technical and behavioral questions from your résumé and the job description, reads them aloud and scores each spoken answer out of ten, so you can rehearse the explanation as well as the code. The free plan gives 15 minutes a day of live help in sessions of up to 15 minutes, with AI mock interviews included. Online assessments and many coding rounds forbid outside help, so practice beforehand and follow your employer's rules on the day.
Disclosure: CoPilot Interview is our product, so weigh what we say about it accordingly.
Frequently asked questions
What programming language should I use in a Juspay interview?
DSA tests and problem-solving rounds usually let you choose a mainstream language such as C++, Java or Python. Hackathon rounds may ask you to work in PureScript or another language Juspay uses, and reports say you learn it on the spot, so time with a functional language beforehand helps.
Does Juspay send an online assessment?
Yes, for campus drives and the Hiring Challenge. The 2025 Hiring Challenge listing on Unstop described a 30-question MCQ round in 30 minutes, then a 90-minute coding test, then interviews; campus reports describe three graph-heavy problems. Our <a href="/blog/hackerrank-assessment-guide">HackerRank assessment guide</a> explains how timed tests work.
Do I need to know Haskell for a Juspay interview?
Candidate reports suggest not. Juspay's stack is built on Haskell and PureScript, but its tests and problem-solving rounds use mainstream languages, and the hackathon rounds that use PureScript are designed for you to learn as you go. Learning the basics of pure functions, immutability, recursion and higher-order functions beforehand still gives you an edge.
How should I prepare for Juspay coding questions?
Practice practical problems under time limits, build small features against an API in your interview language, and prepare one system design in Juspay's domain. Explain every solution out loud, because follow-up questions about trade-offs matter as much as the first answer.
Can I use AI tools in a Juspay interview?
Only if the instructions you receive say so. Online assessments and live coding rounds generally forbid outside help, and some companies now state their AI policy in the invitation. Use AI to practice beforehand, and follow your employer's rules.
Practice this interview before the real one
The AI mock interview builds questions from your resume and the job description, reads them aloud and scores each spoken answer out of 10. Included on the free plan.
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