Introduction

CQRSKit is a TypeScript framework for implementing Command Query Responsibility Segregation (CQRS) and Event Sourcing with clean boundaries, zero runtime dependencies, and fully pluggable database adapters. It’s designed for developers who want a simple but powerful foundation for building event-driven systems without the overhead of large frameworks.

Key Features

• Full CQRS Implementation: Strict separation of commands and queries

• Event Sourcing: Rebuild aggregate state from historical events

• Pluggable Database Adapters: Integrate with any event store (Genesis DB, MySQL, PostgreSQL, etc.)

• TypeScript-First: Full type safety and IDE autocompletion

• Decorator-Based API: Clean, expressive syntax for defining handlers

• State Caching: Optional in-memory LRU cache for performance

• Event Upcasting: Handle schema evolution gracefully

• Async Event Processing: Partitioned background event handling

• Testing Utilities: Fluent Given-When-Then testing API

• Zero Dependencies: Except for database adapters

How It Works

CQRSKit separates write operations (commands) from read operations (queries). Instead of mutating state directly, commands produce events, immutable records of what happened. Aggregates rebuild their state by replaying those events, ensuring complete traceability and easy debugging.

Each change is represented as a fact, a domain event, not as an update in a table. You can always replay history, rebuild projections, or roll back to a point in time.

Why CQRSKit?

CQRSKit focuses on the essentials:

• Declarative configuration through decorators

• Database adapters you can swap at any time

• Designed for testability and composability

• Ideal for microservices and serverless environments

Adapter Support

Adapters can connect CQRSKit to any event store via a simple interface.

Out of the box, it ships with a Genesis DB adapter, with reference implementations for PostgreSQL and in-memory storage.

Ideal Use Cases

• Event-sourced microservices

• Domain-driven design projects

• Systems needing audit trails or replayability

• Prototyping with Genesis DB or PostgreSQL backends

Conclusion

CQRSKit delivers the full power of CQRS and Event Sourcing in a compact, type-safe package, perfect for developers who want to stay in control of their architecture without boilerplate or heavy dependencies.

Learn more on npmjs.com/package/cqrskit and explore examples in the repository.