Updated July 2026. Refreshed for current microservices best practices.
What Is Event Sourcing?
Event sourcing persists state as a sequence of immutable events rather than overwriting current rows. To get today’s order status, you replay all events: OrderCreated, PaymentReceived, OrderShipped. The event log is the source of truth.
Benefits for Microservices
- Complete audit trail — every state change is recorded with timestamp.
- Time travel — reconstruct state at any point for debugging or compliance.
- Natural integration — events feed other services via Kafka.
- Temporal queries — “What was inventory on March 1?” becomes answerable.
Event Store Options
- Apache Kafka — distributed commit log, ideal for high throughput.
- EventStoreDB — purpose-built event store with stream subscriptions.
- PostgreSQL — append-only tables for smaller systems.
Snapshots and Performance
Replaying thousands of events per aggregate is slow. Take periodic snapshots (current state + version number) and replay only events after the snapshot. Kafka log compaction can retain latest record per key for snapshot-like behavior.
CQRS + Event Sourcing Together
Event sourcing typically pairs with CQRS: the event store is the write model; projections build read models. See CQRS with Kafka for the full pattern.
Implementation Checklist
- Define event schemas with versioning strategy (upcasting old events).
- Enforce idempotent event handlers (at-least-once delivery).
- Use correlation IDs across services for tracing.
- Plan GDPR: event deletion vs anonymization policies.
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Kindson Munonye is a software engineer and technical author specializing in microservices, CQRS, event sourcing, and distributed systems. He publishes free step-by-step tutorials and live classes on Alkademy.