> ## Documentation Index
> Fetch the complete documentation index at: https://docs.snakream.tonbo.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Exactly-Once Writes

> See how producer identifiers, epochs, and sequence numbers provide deduplicated appends.

Network retries can cause duplicate appends. Snakream supports producer-level deduplication so your application doesn't have to:

* `Producer-Id`: a stable client identifier (e.g. a UUID)
* `Producer-Epoch`: incremented each time the client restarts
* `Producer-Seq`: a per-epoch sequence number starting at 0

The server tracks these per producer. If a retried append carries the same epoch and sequence, it is silently deduplicated. If there's a gap or epoch regression, the server rejects the write. This gives you exactly-once semantics without application-level bookkeeping.