Append only by design
An immutable ledger never updates or deletes a posting once written. Corrections are made by appending a new reversing entry rather than editing history. This preserves a complete and tamper evident record of what happened.
Why immutability helps
- You get a full audit trail for free because nothing is overwritten.
- Concurrent readers never see a half edited row, which simplifies caching.
- Disputes can be resolved by replaying the exact sequence of events.
Correcting mistakes
If a posting was wrong, you write a reversal that cancels it, then post the correct entry. The original stays visible so auditors can see both the error and the fix.
Storage notes
- Use a monotonically increasing sequence number per entry.
- Optionally chain each entry with a hash of the previous one for tamper evidence.
- Snapshot balances periodically so reads do not scan all of history.
Key idea
A ledger is append only, so you fix mistakes by adding reversing entries, never by editing the past.