# EPOCH_MISMATCH — shard ownership epoch has changed

Shard ownership is tracked by an epoch counter that increments whenever the cluster re-partitions. A write is rejected with this error when the writing no…

<em>cyoda-go version <a href="https://github.com/Cyoda-platform/cyoda-go/releases/tag/v0.6.2">0.6.2</a></em>

# errors.EPOCH_MISMATCH

## NAME

EPOCH_MISMATCH — a node attempted to write to a shard it no longer owns because the cluster epoch advanced.

## SYNOPSIS

HTTP: `409` `Conflict`. Retryable: `yes`.

## DESCRIPTION

Shard ownership is tracked by an epoch counter that increments whenever the cluster re-partitions. A write is rejected with this error when the writing node's cached epoch is stale — another node has since taken ownership of the shard. This prevents split-brain writes.

Retryable. The routing layer re-routes to the current shard owner on retry. Frequent recurrence indicates cluster instability or high re-partitioning frequency.

## SEE ALSO

- errors
- errors.CONFLICT
- errors.TX_CONFLICT

## See also

- [`cyoda help errors`](/help/errors/) — Every error response from the Cyoda REST API carries a structured `errorCode` in the `properties` object. Multiple codes may share the same HTTP status. Programmatic handling keys on `errorCode`, not HTTP status.
- [`cyoda help errors CONFLICT`](/help/errors/conflict/) — The server detected that the entity was modified by another writer between the time it was read and the time the current write was committed. Normal outcome under concurrent load.
- [`cyoda help errors TX_CONFLICT`](/help/errors/tx_conflict/) — The underlying storage detected a serialization failure (e.g., PostgreSQL error 40001 or 40P01) and aborted the transaction. Normal occurrence under concurrent write load when using serializable or repeatable-read isolation.

## Raw formats

- [`/help/errors/epoch_mismatch.json`](/help/errors/epoch_mismatch.json) — full descriptor (matches `GET /help/{topic}` envelope)
- [`/help/errors/epoch_mismatch.md`](/help/errors/epoch_mismatch.md) — body only