Eventual Consistency and the UX

1. The Lag Is a Product Surface

Everything this module has built (events, outboxes, sagas) shares one property. Between the write and the rest of the world knowing about it, there is a lag. Usually milliseconds. Sometimes seconds. During an incident, occasionally minutes.

Engineers habitually treat that lag as an infrastructure detail. It is not. It is a product surface, meaning a part of the system that users touch directly and form opinions about.

Here is how they touch it. A customer updates their shipping address