Hack4Hack Crew Hiring Challenge 2026

About

We are hiring 2 Full-stack Engineers. Instead of a CV filter, show us what you can build. Solve one of two real problems from our product, and the top 5 for each problem statement interview for a paid internship or a full-time job.

Free to enter. Individual. Remote, open worldwide. Starts today.

Problem statements

Pick one. Both are real problems we deal with, and both are hard on purpose: expect 30 to 50 hours of work. Doing the must-haves properly, with honest notes on what is missing, beats doing everything badly.

PS1 · Race-proof team formation at scale

Hundreds of people clicking "join" at the same second. Exactly one gets the last seat.

Your task: Build a production-grade team-formation service for a hackathon with 10,000 participants: teams with invite codes, join requests the leader accepts or declines, and a live "looking for teammates" board. It must stay correct when hundreds of people click at the same moment.

Must have:

• Rules: team size between a minimum and a maximum, one team per person per hackathon, invite codes that expire, leadership passes on when the leader leaves, the last member leaving deletes the team
• Race-proof: 50 people try to take the last seat in a team at the same instant and exactly one gets it. Prove it with an automated concurrency test
• Idempotent: a retried request (double click, flaky network) never joins twice or creates two teams
• Real-time: the board and team pages update live for everyone (WebSockets or server-sent events), no refresh
• Secure: authentication, only the leader can accept, decline or remove; invite codes cannot be brute-forced (rate limits, enough entropy); every input validated
• An audit log of every team change: who, what, when
• Teammate suggestions: an endpoint that ranks people by complementary skills and time zone, with the scoring explained
• Tested and fast: at least 20 API tests, including the race test, running in CI (GitHub Actions). A seed script for 10,000 users and 2,000 teams, and a load test (k6 or autocannon) showing p95 under 200 ms on the board endpoint with 100 concurrent users
• A React UI for the whole flow that works on a phone and with a keyboard only
• Deployed: a live URL on any free tier

Bonus: optimistic UI with rollback on conflict, Docker Compose for one-command setup, tracing or metrics, a chaos test (kill the server mid-join and show nothing is corrupted).

Submit: GitHub repo, live URL, the load-test report, and a 1-page design doc: data model, how you prevent races, the trade-offs you made and what you would do with one more week, plus a walkthrough video of up to 5 minutes.

What we look at: Correctness under concurrency first, then your design decisions and how well you defend them, then code quality, tests and UX.

PS2 · Deadline Crush: submissions that survive the last 10 minutes

Every hackathon gets most of its submissions in the final minutes. Nothing may be lost.

Your task: Build the project-submission system for a hackathon where 2,000 teams submit in the last 10 minutes before the deadline: project details, links and a file of up to 100 MB each. Files go straight to object storage, every submission is checked in the background, and the deadline is enforced fairly by the server, not by the browser.

Must have:

• Uploads: files of up to 100 MB go directly to S3-compatible object storage (MinIO, Cloudflare R2 or similar) through short-lived signed URLs, in resumable chunks: a dropped connection continues where it stopped, and your API server never streams the file
• Deadline: enforced on the server clock. Write down a clear grace policy for uploads that started before the deadline, and enforce it. Teams can edit until the deadline; every version is kept and the last one before the deadline counts
• Background checks: a job queue with workers that verify the file type by its content (not the extension), reject zip bombs and oversized archives, check that the submitted links respond, and make a preview (first page of a PDF or the README of a zip)
• Live status: each team sees its submission move from uploading to checking to accepted or needs a fix, without refreshing
• Exactly once: a worker that crashes mid-job is retried without duplicate results; prove it by killing a worker during a test run
• Secure: only members of a team can submit or see its files, signed URLs expire, and every input is validated
• Organizer dashboard: live counts of submissions, late attempts and failed checks, plus a CSV export
• Load test: simulate 2,000 teams submitting in 10 minutes (k6 or similar). Report p95 API latency (target under 300 ms) and show that no submission is lost
• At least 20 tests running in CI (GitHub Actions)
• Deployed: a live URL on any free tier

Bonus: an emailed receipt with a hash of the submitted file, uploads that resume after the laptop goes offline, virus scanning, a status page for organizers.

Submit: GitHub repo, live URL, the load-test report, and a 1-page design doc: the upload flow, the deadline and grace policy, how jobs stay exactly-once, the trade-offs you made and what you would do with one more week, plus a walkthrough video of up to 5 minutes.

What we look at: Nothing lost and a fair deadline first, then your design decisions and how well you defend them, then code quality, tests and UX.

How it works

1. Register and pick a problem statement. Both are live now.
2. Round 1: Build task, open from today until Sunday 15 Nov, 11:59 PM IST. Build in your own time and submit from your workspace.
3. Top 5 for each problem statement announced on Saturday 21 Nov. The top 50 get written feedback.
4. Interviews, 23 to 26 Nov, at a time that suits your time zone: a walkthrough of your work, a small live change and a conversation about the role.
5. Offers for the 2 roles by Monday 30 Nov.

What you get

• Top 5 for each problem statement: an interview for a paid internship or a full-time job (remote)
• Top 50: written feedback on your submission
• Every complete submission: a certificate

Who can apply

• Anyone, anywhere in the world
• Students (for internships), freshers and working professionals (for full-time roles)
• Individuals only, one problem statement each

Prizes

• Top 5 for each problem statement: Interview with the Hack4Hack founding team for one of 2 Full-stack Engineer roles: a paid internship or a full-time job (remote). Pay and start date are discussed in the interview.
• Top 50: Short written feedback on your submission

Perks

• Free to enter
• 2 Full-stack Engineer openings: paid internship or full-time
• Interviews for the top 5 on each problem statement
• Remote: open to candidates worldwide
• Written feedback for the top 50
• Certificate for every complete submission

Timeline

1. Round 1: Build task (1 Nov 2026 – 15 Nov 2026): Open from today, 1 Nov, until Sunday 15 Nov, 11:59 PM IST. Register, pick one of the 2 problem statements, build it in your own time and submit from your workspace: GitHub repo, live URL, your design doc and load-test report, and a walkthrough video of up to 5 minutes. The tasks are hard on purpose: expect 30 to 50 hours of work.
2. Top 5 per problem statement announced (21 Nov 2026 – 21 Nov 2026): The top 5 for each problem statement are announced on Saturday 21 Nov by email and on this page. The top 50 get written feedback.
3. Interviews (23 Nov 2026 – 26 Nov 2026): A 45-minute online interview with the founding team, at a time that suits your time zone: a walkthrough of your submission, a small live change, then a conversation about the internship or full-time role.
4. Offers (27 Nov 2026 – 30 Nov 2026): We fill 2 Full-stack Engineer roles. Candidates we want to hire hear from us with an offer by Monday 30 Nov.

Rules

1. Open to candidates worldwide. Individual only: one account per person, one submission per person, on one problem statement.
2. Free to enter. Hack4Hack never charges candidates in a hiring challenge.
3. Work on your own. AI coding tools are allowed, but you must be able to explain every line in the interview.
4. Submit before Sunday 15 Nov, 11:59 PM IST. Late submissions are not reviewed.
5. Your work stays yours. We review submissions only to hire and do not use them in our product.
6. Plagiarism or copying another candidate's work leads to disqualification.
7. The top 5 for each problem statement are invited to interview for one of 2 Full-stack Engineer roles: a paid internship or a full-time job (remote). Offers are made at Hack4Hack's discretion after the interviews.

Hack4Hack Crew Hiring Challenge 2026: quick answers

What is Hack4Hack Crew Hiring Challenge 2026?

Hack4Hack Crew Hiring Challenge 2026 is a remote Full-Stack internship & job challenge, organized by Hack4Hack. Skip the CV: solve one real full-stack problem from the Hack4Hack product (React, Node.js, MongoDB) and the top 5 on each problem statement interview for a paid remote internship or a full-time Full-stack Engineer job. Free and individual, for 3rd and 4th-year students, freshers and professionals.

When is Hack4Hack Crew Hiring Challenge 2026?

Hack4Hack Crew Hiring Challenge 2026 runs from 1 Nov 2026 to 30 Nov 2026, online. Registration is open until 15 Nov 2026. Stages: Round 1: Build task (1 Nov 2026); Top 5 per problem statement announced (21 Nov 2026); Interviews (23 Nov 2026); Offers (27 Nov 2026).

What is the last date to register for Hack4Hack Crew Hiring Challenge 2026?

Registration for Hack4Hack Crew Hiring Challenge 2026 closes on 15 Nov 2026 (11:59 pm IST). Register on Hack4Hack before then.

What do the top candidates get at Hack4Hack Crew Hiring Challenge 2026?

2 Full-stack Engineer roles: the top 5 for each problem statement get an interview. Free to enter. 2 Full-stack Engineer openings: paid internship or full-time. Interviews for the top 5 on each problem statement. Remote: open to candidates worldwide.

Is Hack4Hack Crew Hiring Challenge 2026 free?

Yes, registering for Hack4Hack Crew Hiring Challenge 2026 is free.

Who can participate in Hack4Hack Crew Hiring Challenge 2026?

College students, freshers and working professionals can take part, individually. It is fully online, so you can join from anywhere.

Can I join Hack4Hack Crew Hiring Challenge 2026 from outside India?

Yes. Hack4Hack Crew Hiring Challenge 2026 runs fully online, so you can take part from any country unless its rules say otherwise. It starts 1 Nov, 12:00 am IST (31 Oct, 6:30 pm UTC).

Can 3rd-year or final-year students apply to the Hack4Hack Crew Hiring Challenge 2026?

Yes. 3rd-year (2028 batch) and 4th-year (2027 batch) students can apply and usually join as paid interns; 2026 batch freshers and professionals can be hired full-time. The challenge, interviews and role are remote, so it works alongside college.

Is the Hack4Hack Crew Hiring Challenge an off-campus drive for the 2027 batch?

It works like one, but you are selected on what you build, not your CV or a written test. Register, solve one problem statement by 15 Nov, 11:59 PM IST, and the top 5 on each problem statement interview for one of 2 Full-stack Engineer roles. Offers go out by 30 Nov.

Is the Hack4Hack internship paid and remote?

Yes. Both roles are paid and remote: a paid internship for students or a full-time job for graduates and professionals. Pay and start date are discussed in the interview.

What skills do I need for the Hack4Hack Full-stack Engineer role?

React, Node.js (Express) and MongoDB, plus the things production systems need: preventing race conditions, real-time updates with WebSockets or server-sent events, automated tests in CI, load testing (k6 or autocannon), file uploads to object storage and clear design trade-offs. Any stack is fine if you can defend it.

How is a hiring challenge different from a placement drive or coding test?

Instead of a timed DSA test, you build a real, deployed project over two weeks (30 to 50 hours), with a design doc and a short walkthrough video. The interview is about your own code: you walk the team through it and make a small live change.

Does the Hack4Hack Hiring Challenge help with placements if I am not hired?

Yes. You finish with a production-grade full-stack project, a live URL and a load-test report to show recruiters, a certificate for a complete submission, and written feedback if you are in the top 50.

Is the Hack4Hack Crew Hiring Challenge genuine? Do I have to pay?

It is run by Hack4Hack to hire 2 Full-stack Engineers for its own team. It is free at every stage: Hack4Hack never charges candidates in a hiring challenge, and your code stays yours.

Frequently asked questions

Is it free?

Yes. Hiring challenges on Hack4Hack are always free for candidates.

Which role is open?

Full-stack Engineer. We are hiring 2 people, as paid interns or full-time. You pick one of 2 problem statements: PS1 Race-proof team formation at scale, or PS2 Deadline Crush, a submission system that survives the last 10 minutes.

What do I get?

The top 5 for each problem statement interview with our founding team. The top 50 get written feedback. Everyone with a complete submission gets a certificate.

Internship or full-time?

Both are open. Students usually join as paid interns; graduates and professionals can be hired full-time. You tell us which you want in the interview.

Who can apply? Is it remote?

Anyone, anywhere in the world. The challenge, the interviews and the roles are remote, and interviews are scheduled to suit your time zone.

How hard is it?

Hard on purpose. Expect 30 to 50 hours of work over the two weeks. We would rather see the must-haves done properly, with honest notes on what is missing, than everything done badly.

Which stack must I use?

We use React, Node.js (Express) and MongoDB, so that is ideal, but any stack is fine if you can defend your choice.

Can I use AI tools?

Yes, like you would at work. The tasks are built so that AI alone is not enough: race conditions, load tests and design trade-offs. In the interview you walk us through your code and make a live change, so make sure you understand all of it.

Do you keep my code?

No. Your work stays yours. We look at it only to decide who to interview.

Can I solve both problem statements?

No. Pick one, so we see your best work.