Redux on the Server: Building a Node.js Event Sourcing Library

CRUD alone struggles with requirements that need context around state changes, such as approvals, edit history, or rollbacks. Storing only the current state makes it hard to trace "why it ended up this way," and as features grow, tables and logic become increasingly complex.

As an alternative, Event Sourcing was chosen. Instead of overwriting state directly, every event that changed the state is stored, enabling audit logs, reconstruction of past points in time, easy rollbacks, and analysis of data changes.

The core concept is very similar to Redux, which frontend engineers are already familiar with. Just as Redux computes state using Action and Reducer, event sourcing computes the next state by replaying events in order. The difference is that while Redux operates in browser memory, event sourcing permanently stores that record in a DB.

The library built to make this pattern easy to use in a TypeScript environment is Ventyd. It had three goals:

• Familiar like Redux: so frontend and Node.js developers can understand it immediately
• TypeScript-first: prioritizing type safety above all
• Flexible: not tied to a specific DB or validation library

The usage pattern involves defining events and the final state with schema, computing state changes per event with reducer, and putting business methods in the Entity class. Finally, in the Repository, adapters and plugins are connected to attach features like DB storage, audit logs, and notifications. For validation libraries, not only Valibot but also Zod, TypeBox, ArkType, and others can be used.

As real-world use cases, a frontend deployment platform recorded the entire process—deployment start, build, test, deploy, and rollback—as events, improving traceability and notifications. Also, in game state management, the same Entity and logic were used together on the client and server, achieving immediate local responsiveness, offline support, server-side validation, and replayability.

In summary, Ventyd is a tool for Node.js / TypeScript that lets you handle event sourcing like Redux. It enables frontend and backend to discuss domain logic using a common language of Schema, Event, Reducer, Entity, and Repository, and helps make complex internal tooling more transparent and extensible.