event driven

Queue, log and router solve different problems that all get called events. Picking by workload shape beats picking by whichever service the team already knows.

Orchestration buys a visible state machine with declared retries; choreography buys independence and coupling debt. Money paths usually deserve the state machine.

A dead-letter queue with no owner is a landfill with a nicer name. Triage discipline separates teams that recover messages from teams that archive regret.

Utilization-based scaling is the wrong sensor when work arrives as backlog. The design questions are threshold math against drain rate, reaction-time bounds from polling, and why lag-driven fleets oscillate without generous targets and idempotent consumers.

There is no status code and no caller waiting, so latency and error rate stop meaning what they meant. The signals that replace them are age, lag and completion, and they answer a question the request-response set never had to ask.