Problem Statement
Event Sourcing is a data storage pattern where you save every state-changing event that happens in your system, instead of saving just the current state. You might encounter this need when your traditional CRUD database starts feeling like a bottleneck—maybe you’re losing audit trails, struggling to debug complex workflows, or needing to replay past states for machine learning or compliance. Sound familiar? It’s the kind of problem that creeps up once your app grows past a simple to-do list.
Core Explanation
Event Sourcing flips your mental model upside down. Instead of updating a row in a database (like changing a user’s email from “old@example.com” to “new@example.com”), you append an event to an immutable log: “User changed their email from X to Y.” The current state of that user is then derived by replaying all events that have ever happened for them.
Here’s how it works in practice:
