Rupen Patel Most enterprise systems can tell you what they believe right now. Far fewer can prove what they believed last quarter, why they made a given decision, and who was authorized to make it. That gap is what I build for. What Factum is Factum is a Java/Spring Boot SDK for event-sourced systems of record. Instead of overwriting state and hoping the logs are enough, applications built on Factum keep an immutable, replayable record of every decision — with bi-temporal modeling so late-arriving facts and retroactive corrections don't destroy your history, and a fine-grained entitlements engine so authorization decisions are as auditable as the data itself. It embeds in the JVM. No new cluster to operate, no rip-and-replace, no platform migration to get value from the first bounded context. Why it matters, depending on where you sit • Banking & capital markets — reconstruct the full lifecycle of a trade, a limit change, or a customer decision, on demand • PBM & health plans — show exactly why a claim adjudicated the way it did, under the eligibility and formulary in effect that day • Airlines — replay an IROPS cascade decision by decision instead of reverse-engineering it from logs •