---
title: "Straightforward Event Sourcing with TypeScript and NodeJS"
url: https://daily.dev/posts/straightforward-event-sourcing-with-typescript-and-nodejs-nx6bc6muk
source_url: https://event-driven.io/en/type_script_node_Js_event_sourcing
type: article
source: "Event-Driven by Oskar Dudycz"
published: 2026-06-17T11:26:19.291Z
updated: 2026-06-17T11:33:25.964Z
tags: ["architecture", "nodejs", "typescript"]
reading_time: 15
upvotes: 0
comments: 0
language: en
---

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# Straightforward Event Sourcing with TypeScript and NodeJS

**[Event-Driven by Oskar Dudycz](https://daily.dev/sources/event-driven-io)** · 15 min read · 0 upvotes · 0 comments

## Summary

A practical walkthrough of implementing Event Sourcing in TypeScript and NodeJS using the Decider pattern. Covers defining union types for events, commands, and state; building an evolve function for state reconstruction via event reduction; implementing a decide function for business logic; and composing a full HTTP API with ExpressJS using curried command handlers, optimistic concurrency via ETags, and EventStoreDB as the event store.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://event-driven.io/en/type_script_node_Js_event_sourcing>

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Tags: [#architecture](https://daily.dev/tags/architecture), [#nodejs](https://daily.dev/tags/nodejs), [#typescript](https://daily.dev/tags/typescript)

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