Repair Stream Backpressure Failures

Our Node/TypeScript export service reads PostgreSQL rows as an async iterator, enriches them, compresses the result, and streams a ZIP to the HTTP response. The enrichment stage starts work without awaiting capacity, so 30k–80k promises can be in flight. When a client downloads slowly, memory rises above 2 GB. On disconnect, enrichment continues and the DB iterator closes late. Repair backpressure and cancellation locally with generated rows and fake enrichment. Preserve row order and every row. Do not query production, change proxy settings, drop records, or invent a new memory limit.

Backpressure failure found. Unbounded enrichment creates excessive in-flight work and slow downstream consumption lets results accumulate. The repair adds bounded concurrency, downstream pressure propagation, ordered release, cancellation-aware cleanup, deterministic pressure tests, and in-flight metrics. Production capacity remains unverified.