What is Eventstore?

Sliceworkz Eventstore is an open source eventstore implementation in Java.

• If’re you’re into eventsourcing, have a look at our quickstart guide and documentation to get started.
• If you’re new to eventsourcing, do yourself a favor and learn about it

Features

• Fully compliant with DCB, the Dynamic Consistency Boundary specification
• Fully typed access to Event via EventStreams, checked by the compiler
• Event Query capabilities on event Types and Tags, with a fluent builder and paged reads
• Optimistic locking on Event appends, atomic under concurrency, with head() to pin a boundary before deciding
• Built-in upcasting of legacy events, across chains of versions
• Stored event names decoupled from class names with @EventName
• Idempotent appends scoped per event stream, a batch de-duplicated as a unit
• Bookmarks with a read position — a reader resumes from the last event it handled, and its lag is counted from how far it has read — even before it has handled anything
• Import and migration between storage backends, preserving event identity
• Leader election on named leases, with fencing tokens and priority-based handover
• GDPR erasure by crypto-shredding — personal data encrypted per data subject, erased by destroying keys, never by rewriting events
• Reader entitlement — services that may not see personal data read the events with it withheld

Technical

• Pure Java implementation
• Lightweight with minimal dependencies — the API carries SLF4J and no metrics library; every jar declares an Automatic-Module-Name
• Postgres-based database storage — PostgreSQL 16+ supported, with native server-side uuidv7() on 18+ and a Java-side fallback on 16–17 (auto-detected at startup)
• In-Memory storage for development and unit-testing
• File-persisted in-memory storage for local development without PostgreSQL
• Explicit lifecycle: storage, store and stream are all AutoCloseable
• Observability through an SPI of its own — bind Micrometer, OpenTelemetry or anything else with an EventStoreObserver
• Measured performance — a benchmark suite behind every design choice, from stream layout to the shape of the consistency check
• Published test module: a given/when/then fixture for applications, and a TCK for custom storage backends