Event Sourcing

Stores your application state as an immutable sequence of events instead of just the current state, which means you can rebuild state at any point in time, run temporal queries, and get full audit trails for free. The skill covers event stores, aggregates, CQRS projections, and includes practical implementations in TypeScript and PostgreSQL. Use this when you need audit compliance, are building financial systems, or want to debug by replaying past states. The concurrency control and snapshot examples are solid, though you'll need to think hard about event schema evolution before you're in production. Fair warning that querying gets more complex since you're reading from projections instead of your source of truth.

skills.sh installs: 892
GitHub stars: 379
last updated: Aug 21, 2026

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Install

$ npx -y skills add aj-geddes/useful-ai-prompts --skill event-sourcing --agent claude-code

Installs into .claude/skills of the current project.

Files

Overview

Store state changes as a sequence of events rather than the current state, enabling temporal queries, audit trails, and event replay.

When to Use

Audit trail requirements
Temporal queries (state at any point in time)
Event-driven microservices
CQRS implementations
Financial systems
Complex domain models
Debugging and analysis
Compliance and regulation

Quick Start

Minimal working example:

interface DomainEvent {
  id: string;
  aggregateId: string;
  aggregateType: string;
  eventType: string;
  data: any;
  metadata: {
    userId?: string;
    timestamp: number;
    version: number;
  };
}

interface Aggregate {
  id: string;
  version: number;
}

class EventStore {
  private events: DomainEvent[] = [];

  async appendEvents(
    aggregateId: string,
    expectedVersion: number,
    events: Omit<DomainEvent, "id" | "metadata">[],
// ... (see reference guides for full implementation)