Event Sourcing
Event sourcing is a pattern where every change to application state is stored as an immutable event in an append-only log, rather than overwriting the current state. The current state is derived by replaying the events.
Storing events instead of state
In a traditional system, you store the current state and overwrite it as things change. You know the balance is 100, but not how it got there. Event sourcing flips this: you store every event, the deposit, the withdrawal, the correction, and compute state by replaying them.
The benefits are a complete audit trail, the ability to reconstruct state at any past point, and the freedom to build new views of the data after the fact. The cost is that you store a lot of events, which is itself a high-volume, append-only, timestamped workload.
That event log is, in effect, time-series data, and it benefits from the same kind of storage.
How Arc handles Event Sourcing
An event log is append-only timestamped data, exactly what Arc stores well. Arc keeps the full event history as compressed Parquet you can query and replay with SQL, without the cost pressure to prune old events.
Related terms
Arc is a high-performance columnar database. Open Parquet on storage you own, single Go binary, production-ready in 30 seconds.