Senior TypeScript/Node Engineer

mxtape sells a physical product: custom acrylic music cards with NFC — tap a phone and the playlist plays. Our AI Studio (customers generate their cover art) is live and recently rebuilt; this contract is engine internals only — no UI, no greenfield. The full scope is in the attached RFP as 6 separately-priced workstreams. Highlights: Print-quality tier: high-quality re-render / AI upscale of the purchased cover (socket already built) Variety system: re-roll modes + cross-slot diversity enforcement Speed & API cost: planner latency, prompt caching, spend telemetry One production bug: a Vercel serverless cold-start crash to root-cause Hardening: rate limiting, tests + CI, observability Stack: TypeScript end-to-end · Vercel serverless functions (Node ESM) · OpenAI (gpt-5 planner + gpt-image-2, SSE streaming) · Firebase (Firestore/Storage) · React 18 + Vite (read-only context) You: shipped production LLM/image-gen pipelines (show two); strong on serverless streaming, cost-aware API design, and writing testable code. You read the RFP and quote per workstream — we accept any subset. Milestone escrow tied to demonstrated acceptance criteria on staging, PRs reviewed before release. US-overlap communication, demos at checkpoints. To apply: per-workstream price + hours, your build order and why, and anything in the RFP you'd challenge — we respect pushback with reasoning. (RFP attached) , link to mxtape studio provided when we chat.