System Design Patterns: From Fundamentals to Real Systems
Vote

0% completed

​

Exactly-Once Semantics

1. The Incident

The store meters partner API usage and bills for it: a streaming job counts each partner's calls per day and feeds invoices. It is the most money-sensitive pipeline in the company, and it has been quietly wrong in both directions.

Month one: overbilling. A routine crash-and-rewind (the stream lesson's ordinary recovery) reprocessed forty minutes of events, and the running counts absorbed them twice. Partner A was billed for 1,041 calls; their own logs show 987. They audited

.....

.....

.....

Like the course? Get enrolled and start learning!