CodeRelay is a fast, social way to practice algorithms and data structures. Players join a live room, pick a challenge, write code in the`` browser, and watch rankings update in real time. It’s built for bootcamps, university clubs, engineering teams, and streamers who want competitive energy without setup headaches.

What makes it fun

• Live leaderboard: Rankings update instantly as submissions pass tests (no page refreshes).

• 1v1 duels: Head-to-head matches—first Accepted wins (or best score at the buzzer).

• Time-attack mode: A visible countdown adds pressure and drama.

• Spectator links: Share a room URL so viewers can watch the match live.

• Fair play by design: Code runs server-side in isolated, short-lived containers with strict limits.

How it works

1. Join a room (solo, group, or 1v1) — or share a link for spectators.

2. Read the problem, code in the browser, and submit.

3. The platform spins up a fresh container, evaluates your solution, and pushes results to everyone in the room in real time.

4. When the timer ends, winners and detailed results are announced.

Technology overview

• Frontend: React with Monaco Editor for a familiar, VS Code–like experience; real-time updates via WebSockets (two-way communication—no polling). (Microsoft GitHub)

• Backend: Go for low-latency rooms and judging.

• Database: SQLite (embedded, zero-config) for users, problems, submissions, and scores—great for a lean MVP. (SQLite)

• Sandboxed execution: Each submission runs in an ephemeral Docker container with CPU/RAM/time limits and seccomp syscall filtering; hardening options like gVisor can be added in production. (Docker Documentation)

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Developer setup

• Go: go1.22.5 (pinned via toolchain in backend/go.mod).
• Node.js: 22.14.0 (see .nvmrc and frontend/package.json).
• Install dependencies once with make frontend-install.
• Run the API locally with make backend-run; stop with Ctrl+C.
• Execute backend checks via make backend-test, make backend-fmt, and make backend-lint.
• Build or lint the UI with make frontend-build and make frontend-lint.
• Bring the full stack up using make compose-up (wraps docker compose up --build).
• Inspect container readiness with docker compose ps and tail service logs via docker compose logs -f api.

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MVP

Scope

• Single room, single problem

• One language: Python (start simple; add more later)

• User accounts with nickname + password login (stored in SQLite)

• WebSockets for live leaderboard & submission status (replace polling)

• Verdicts: AC, WA, TLE

• First AC wins (tie breaks on earliest AC time)

Tech Stack

• Backend: Go (REST + WebSocket), single judging worker

• Database: SQLite

• Frontend: React + Monaco

• Containers: Docker Compose (api, frontend); SQLite lives on a volume

Database (initial)

• Migrations: users, problem, test_case, submission

• Seed: 1 demo problem + 5–10 hidden tests

• Basic indexes for smooth reads (e.g., submission(created_at))

Backend (behavior)

• Submission lifecycle: queued → running → AC/WA/TLE

• Single worker: fetch next queued submission, run tests, persist verdict/runtime

• Live updates: push submission results & leaderboard over WebSocket

Runner (idea level)

• Auto-launch a fresh container per submission

• Feed test input via stdin, capture stdout/stderr

• Enforce time and memory limits; no network; cleanup always

• Map outcomes to AC/WA/TLE

  • Use Docker resource controls and the default seccomp allowlist for syscall reduction

Frontend

• Authentication screen (login/register with nickname + password)

• Problem view (markdown statement + samples)

• Editor + Submit button (Monaco)

• Live results panel (WebSocket)

• Leaderboard + countdown timer (synced to server clock)

DevOps

• Dockerfiles for api/frontend

• Compose with volumes for code, SQLite db, and problem assets

• Health checks; one-command local run

Testing

• Happy path: AC submission appears on leaderboard

• WA and TLE cases

• Concurrent submissions from two browsers (leaderboard updates in real time)

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Extras (nice to have)

• Elo rating for 1v1 and arena modes (simple K-factor to start).

• “Code preview” opt-in for players who want to share live progress with spectators.

• Weekly mini-tournaments and season stats.

Team Members

• Bruna Pierobon
• Julia Correia Bindi
• Ömer Duran
• Deniz Can Çalkın