Building a Production-Ready Event Store in PostgreSQL: Schema Design, Projections, and Replay

Your microservice just corrupted production data. A race condition in the order processing service double-charged 847 customers, and now you're staring at a database that only knows the current state of each account. The CFO wants to know exactly which transactions were affected. Legal needs an audit trail. Your on-call engineer is asking the impossible question: "Can we just roll it back?" You can't. Your database doesn't remember what happened—only what is . Every UPDATE statement overwrote the previous truth, leaving you with forensic breadcrumbs scattered across application logs, if you're lucky enough to have logged the right things. This is the moment every engineer wishes they had implemented event sourcing from the start. Event sourcing flips the traditional model: instead of storing current state and discarding history, you store every state change as an immutable event. Your account balance becomes a projection derived from a sequence of deposits, withdrawals, and adjustments