TeamForge
Race-proof team formation for hackathons — 50 people race for the last seat and exactly one gets it, proven by test.
Built at Hack4Hack Crew Hiring Challenge 2026
Team Asmit Sarkar: Asmit Sarkar
Built with Node.js, Express, MongoDB, Mongoose, Socket.io, React, Vite, Jest, autocannon, Docker
About the project
TeamForge is a production-grade team-formation service for a hackathon with 10,000 participants. Teams of 2–4 with expiring invite codes, leader-approved join requests, and a live "looking for teammates" board. Correctness under concurrency is the core: joins run in MongoDB transactions with an atomic conditional seat check, so 50 concurrent joiners for the last seat produce exactly 1 winner and 49 clean 409s (proven by an automated test, run 3x). Mutations are idempotent via Idempotency-Key, every team change is written to an audit log in the same transaction, and teammate suggestions rank people by complementary skills (60%) + timezone overlap (40%) with the formula explained. The React UI is responsive on desktop, laptop, tablet and mobile, and keyboard-only usable, with optimistic join + rollback on conflict and live Socket.io updates. Verified: 36 API tests green, seed of 10,000 users + 2,000 teams in 3.3s, board load test p95 72.3ms at 100 concurrent users (target <200ms), chaos test (SIGKILL mid-join) passes with no corruption. Stack: Node.js, Express, MongoDB (Mongoose), Socket.io, React, Vite.