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#event-sourcing

2 stories

Banner: four event-driven architecture patterns shown as four connected service diagrams

Engineering Practice

Event-driven architecture patterns: notification, state transfer, event sourcing, CQRS

John Nguyen · Jul 12, 2026 · 8 min read

Event-driven is not one pattern but four, and teams get hurt when they mix them up. We compare event notification, event-carried state transfer, event sourcing and CQRS on one billing example, with the costs each one adds and the signals that tell you which fits.

Banner: a single database row with a long trail of faded earlier versions stretching behind it

Databases

Current state is right but history is lost: audit and history data modeling patterns

John Nguyen · Jul 4, 2025 · 10 min read

An order says COMPLETED, but nobody can say what it was before, who changed it, or when. We compare status history tables, trigger-based audit logs, temporal rows and event sourcing, with a runnable Postgres example and the rule we use to pick one.