Senior Full-Stack Engineer (FastAPI • MongoDB • React)

Contribute 15–25 hours per week on a production web application with real-time features, subscriptions, and AI-assisted workflows. The stack uses FastAPI, Motor/MongoDB, httpx, WebSockets, Pydantic, Stripe Checkout, JWT/OIDC auth, and a React SPA with Tailwind.

• Design and maintain FastAPI HTTP and WebSocket endpoints.
• Implement auth flows with passlib/bcrypt, JWT (python-jose), and Google OIDC (Authlib).
• Model and validate data with Pydantic; operate MongoDB via Motor (AsyncIOMotorClient).
• Orchestrate scheduled/background jobs using asyncio.create_task (refreshers, monitors, results processing, daily tasks).
• Build subscription logic and plan limits (Free, Premium Monthly, Premium Yearly).
• Integrate Stripe Checkout through the in-repo wrapper; add idempotent webhooks and lifecycle handling.
• Deliver persona-aware chat features through internal LLM modules; persist sessions and messages.
• Apply robust timezone handling with zoneinfo and pytz.
• Ship targeted fixes and small features in the React SPA (Tailwind, PostCSS, CRACO); maintain token refresh and localStorage hygiene.
• Add logging, metrics, and data-freshness checks; write nightly handover notes.

• 4+ years in Python with FastAPI or Starlette and async I/O.
• Experience with WebSockets, background jobs, and idempotent task design.
• Proficiency with MongoDB schema design, Motor, and Pydantic.
• Production experience with password hashing, JWT, OAuth/OIDC, sessions, CORS/CSRF.
• Hands-on Stripe Checkout or comparable subscription systems.
• React proficiency with REST/WebSocket integrations and token management.
• Sound knowledge of timezone utilities and serialization.

• Work with multi-provider external APIs and failover patterns.
• Delivery of LLM-backed functionality and prompt design.
• Familiarity with Tailwind, CRACO, and PostCSS.
• Practice with observability, incident response, and secure secrets handling.
• Exposure to CI/CD and containerized deployment.

• Night shift aligned to North American evenings/nights; 15–25 hours per week.
• Independent contractor engagement; remote.

• p95 API latency under target thresholds across odds and results endpoints.
• WebSocket stability with high uptime and automatic reconnection strategies.
• Accurate subscription enforcement and low payment failure rates; reliable webhook handling.
• Data freshness SLAs met for each league provider with graceful failover paths.
• LLM chat reliability with safe prompt design and durable session storage.

• Write clear design docs and PRs with explicit acceptance criteria.
• Coordinate with product and design to scope features for the React dashboard and chat UX.
• Document internal modules (emergentintegrations.*) for reuse and onboarding.

• Backend: FastAPI, Starlette, Motor, Pydantic, httpx, Authlib, python-jose, passlib/bcrypt, asyncio.
• Payments: Stripe Checkout (custom wrapper), plan limits in code.
• AI: OpenAI models via internal chat engine with persona prompts.
• Data: The Odds API; league APIs listed above with provider fallbacks.
• Frontend: React SPA, Tailwind, PostCSS, CRACO; tokens in localStorage; AuthContext refresh.
• Time: zoneinfo (America/New_York), pytz.

Send a short portfolio or repo links that demonstrate:

• A FastAPI service with async jobs or WebSockets.
• A React SPA that consumes WebSockets and handles token refresh.
• Any Stripe subscription or LLM integration work.