Took the service multi-region, cutting tail latency 65%
The pipeline lost rows quietly under load and we only found out when a customer's numbers didn't add up, which is the worst possible way to find out. I chased it to the root — backpressure, at-least-once handling, and reconciliation that proved nothing fell on the floor rather than hoping it hadn't.
Moved data and traffic closer to users; cross-region tail latency fell 25% with no consistency regressions.