EventStoreDB Event Sourcing Database

EventStoreDB is an open-source event sourcing database designed specifically for building event-sourced systems, providing a reliable, high-performance store for immutable event streams. Originally created by James Nugent and Greg Young in 2012, the project has over 5,300 stars as of 2026 and is available in both Community (open-source) and Cloud editions. Key features include: event streams (storing data as immutable sequences of events, each containing event ID, stream ID, event type, data payload, and metadata, with optimistic concurrency via expected version numbers), append-only storage (events are never modified or deleted, providing a complete audit trail and enabling temporal queries to reconstruct state at any point in time), projections (built-in JavaScript projection engine for creating read models, stream transformations, and event filtering, supporting continuous, one-time, and transient projections), subscriptions (persistent subscriptions with competing consumers and consumer group strategies for message distribution, and volatile subscriptions for real-time event notifications), gRPC and HTTP APIs (reading, appending, and subscribing to streams via protocol buffers over gRPC or RESTful HTTP), stream metadata (per-stream metadata including ACLs, maximum age, maximum count, and truncation markers), clustering (multi-node clusters with Raft consensus for strong consistency, automatic leader election, and data replication across nodes), user management (built-in user accounts and groups with role-based access control for stream-level permissions), SSL and TLS (encrypted client-server communication with certificate-based authentication), checkpointing (tracking consumer position for exactly-once processing semantics), and cloud-native deployment (Docker, Kubernetes Helm charts, and managed EventStoreDB Cloud).