The interface is only half the work.

I own the API and database; Samuel owns the dashboard. An OpenAPI contract and generated-type drift checks let us develop the two halves against the same agreement.

CI checks lint, contracts, types, tests, and builds. Actions are pinned to commit SHAs with read-only default permissions. A dependency policy checks publishing age and trust changes before accepting new packages.

The trade-off: a contract needs maintaining. The benefit is catching a broken agreement before it reaches the other developer.

My Flutter and Supabase app includes a push sender with lease-token batch claiming, renewal during processing, and a conditional finish. If another run takes over a row, the old worker cannot mark it complete.

A fake-clock test runs two workers concurrently. Retryable provider errors and a bounded execution time are part of the design, rather than happy-path assumptions.

The trade-off: retries can duplicate delivery. Lease ownership protects state; it does not create an exactly-once guarantee at an external provider.

I built an interactive statistics course with worked examples, guided attempts, saved notes, and practice scoring. Plain JavaScript modules keep the teaching experience independent of a UI framework.

Personal-key access uses per-lesson AES-256-GCM keys derived with HMAC, signed tokens, timing-safe comparisons, and a Redis mutex around device slots. Rate limits account for campus Wi-Fi and carrier NAT, where many legitimate students share an IP.

The trade-off: custom access control keeps dependencies low but increases review responsibility. Encryption alone does not prevent an authorized reader from copying content; device limits also need a humane recovery path.