Materialize/doc/user/shared-content/resize-cluster-for-snapshotting.md

ALTER CLUSTER <cluster_name> SET ( SIZE = <new_size> );

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Resizing a cluster with sources requires the cluster to restart. This operation incurs downtime for the duration it takes for all objects in the cluster to hydrate.

You might want to let the new-sized replica hydrate before shutting down the current replica. See zero-downtime cluster resizing about automating this process.

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Once the initial snapshot has completed, you can resize the cluster for steady state.