[[img-distrib-update]]
.Partial updates to a document
image::images/04-04_update.png[“Partial updates to a document”]

Below we list the sequence of steps used to perform a partial update on a
document, as depicted in <>:

1. It forwards the request to Node 3, where the primary shard is allocated.

The API also accepts the routing, replication, consistency and
timeout parameters that are explained in <>.

When a primary shard forwards changes to its replica shards, it doesn’t
forward the update request. Instead it forwards the new version of the full
document. Remember that these changes are forwarded to the replica shards
asynchronously and there is no guarantee that they will arrive in the same
order that they were sent. If Elasticsearch forwarded just the change, it is
possible that changes would be applied in the wrong order, resulting in a
corrupt document.