Tagged event-sourcing
2 pieces
- · 10 min read
Temperature Zero Is Not Deterministic
Event sourcing assumes you can replay the source and get the same derived state. A model call in the derivation breaks that assumption, because the lowest temperature setting reduces variation without eliminating it, and providers document this. A model-derived layer cannot be regenerated by replay, so the output and the model version have to be stored as part of the record.
- · 11 min read
Model the Trade, Not the Screens
When quote, acceptance and settlement exist as three screens calling services ad hoc, the acceptance and the trade record can disagree, and a double tap can execute twice. An explicit state machine with defined transitions makes the impossible combination unrepresentable rather than merely unlikely. An append-only record of transitions lets settlement and reporting be projections of one history instead of two copies that drift apart.