Intro

EquinoxJS is a TypeScript event sourcing library built around deciders, folds, services and reactions. It is a ground-up re-implementation of the Equinox project from F#.

EquinoxJS is aimed at teams that want a small set of event sourcing primitives with clear operational boundaries. The core library stays focused on deciders, services, reactions and stores rather than introducing a framework around them.

If you already know event sourcing, the main promise is straightforward: EquinoxJS gives you the important pieces needed to build production systems without wrapping the domain in handler abstractions, workflow runtimes or framework glue.

The docs currently cover two primary production paths:

• PostgreSQL via MessageDB
• Serverless deployments via DynamoStore

It also includes the pieces needed for common event sourced application patterns, so the library scales from a single service to more involved systems:

• Read models and projections
• Inline projections for MessageDB
• Process managers and reactions
• A worked hotel group checkout example

When not to use EquinoxJS

EquinoxJS is not for every team or every service.

You should probably look elsewhere if:

• you want a framework that prescribes command handlers, transport wiring and application structure end to end
• you are not actually committed to event sourcing and mostly want straightforward CRUD with an audit trail
• you need multi-stream transactional workflows to be hidden behind a single write API
• your team does not want to reason explicitly about ordering, concurrency, idempotency and replay

EquinoxJS works best when those tradeoffs are acceptable and you want the core event sourcing mechanics to stay visible.