Packages

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Emmett is organized as a modular monorepo. Install only what you need.

Core Package

@event-driven-io/emmett

The foundation of the Emmett ecosystem. Required for all projects.

npm install @event-driven-io/emmett

Provides:

• Event and Command type definitions
• Decider pattern implementation
• In-memory event store for testing
• Command handling utilities
• Projection building blocks

📦 npm · GitHub · README

Event Store Packages

Choose one based on your infrastructure needs.

@event-driven-io/emmett-postgresql

Production-ready PostgreSQL event store with Pongo integration.

npm install @event-driven-io/emmett-postgresql

Features:

• Inline and async projections
• Pongo document database integration
• Full ACID transactions
• Background message consumers

📦 npm · GitHub · Docs

@event-driven-io/emmett-esdb

EventStoreDB integration for native Event Sourcing.

npm install @event-driven-io/emmett-esdb

Features:

• Persistent subscriptions
• Global event ordering
• Built-in projections
• Optimized for Event Sourcing

📦 npm · GitHub · Docs

@event-driven-io/emmett-mongodb

MongoDB event store with flexible storage strategies.

npm install @event-driven-io/emmett-mongodb

Features:

• Single or multi-collection storage
• Document-per-stream option
• MongoDB aggregation pipelines
• Atlas-compatible

📦 npm · GitHub · Docs

@event-driven-io/emmett-sqlite

Lightweight SQLite event store for development and embedded apps.

npm install @event-driven-io/emmett-sqlite

Features:

• File-based or in-memory
• Zero configuration
• Fast test execution
• better-sqlite3 powered

📦 npm · GitHub · Docs

Web Framework Packages

@event-driven-io/emmett-expressjs

Express.js integration with testing utilities.

npm install @event-driven-io/emmett-expressjs

Features:

• Application factory
• Problem Details (RFC 9457)
• ETag concurrency handling
• ApiSpecification for testing

📦 npm · GitHub · Docs

@event-driven-io/emmett-fastify

Fastify integration with plugin architecture.

npm install @event-driven-io/emmett-fastify

Features:

• Plugin-based setup
• Schema validation
• Graceful shutdown
• Fastify inject testing

📦 npm · GitHub · Docs

Testing Package

@event-driven-io/emmett-testcontainers

TestContainers integration for E2E testing.

npm install -D @event-driven-io/emmett-testcontainers

Features:

• Pre-configured containers for PostgreSQL, MongoDB, EventStoreDB
• Docker Compose integration
• Automatic cleanup
• CI/CD optimized

📦 npm · GitHub

Utility Package

@event-driven-io/emmett-shims

Polyfills for environments without native support.

npm install @event-driven-io/emmett-shims

Features:

• AsyncIterator support
• Environment detection
• Edge runtime compatibility

📦 npm · GitHub

Package Compatibility

All packages follow semantic versioning. Major versions are released together to ensure compatibility.

Package	Current Version	Node.js
emmett		≥18.0
emmett-postgresql		≥18.0
emmett-esdb		≥18.0
emmett-mongodb		≥18.0
emmett-sqlite		≥18.0
emmett-expressjs		≥18.0
emmett-fastify		≥18.0
emmett-testcontainers		≥18.0
emmett-shims		≥18.0

Typical Project Setup

API with PostgreSQL

npm install @event-driven-io/emmett \
            @event-driven-io/emmett-postgresql \
            @event-driven-io/emmett-expressjs

npm install -D @event-driven-io/emmett-testcontainers

API with EventStoreDB

npm install @event-driven-io/emmett \
            @event-driven-io/emmett-esdb \
            @event-driven-io/emmett-fastify

npm install -D @event-driven-io/emmett-testcontainers

API with MongoDB

npm install @event-driven-io/emmett \
            @event-driven-io/emmett-mongodb \
            @event-driven-io/emmett-expressjs

npm install -D @event-driven-io/emmett-testcontainers

Related Projects

Pongo

PostgreSQL as a Document Database with MongoDB-like API.

npm install @event-driven-io/pongo

📦 npm · GitHub

See Also

• Getting Started - Complete tutorial
• Choosing an Event Store - Detailed comparison
• Samples - Working examples