Our trading dashboards queried a nightly warehouse and were always hours behind. We moved to Kafka, Flink SQL and Apache Doris: exactly-once ingestion into merge-on-write tables, pre-aggregated minute metrics and partitioning that keeps dashboard queries well under a second.
We added a logging middleware to a FastAPI service and a server-sent events endpoint stopped streaming smoothly: events arrived in bursts, timings were wrong and disconnects went unnoticed. The middleware used BaseHTTPMiddleware. Why it interferes, and how pure ASGI middleware fixes it.
After we turned on streaming for our assistant, tool calls failed with JSON parse errors and sometimes ran with another call's arguments. We were parsing argument fragments per chunk and keying them by arrival order. Accumulating by index fixed it.
Our orders export worked for every customer until one crossed 500,000 rows and PHP died with Allowed memory size exhausted. The endpoint loaded everything with get(), then built the CSV in memory. Streaming keyset chunks straight to the response fixed it at a flat 40 MB.
Our chat assistant streamed tokens smoothly on localhost but in production the whole answer appeared after 14 seconds. nginx was buffering the event stream and gzip was holding bytes. How we proved it with curl and fixed it without breaking other routes.
Our enrichment consumers rebalanced every few minutes, lag climbed past two million messages and some records were processed twice. A slow external API pushed batch processing past max.poll.interval.ms. How we proved it, fixed the poll loop and made rebalances cheap.