In addition to the shard placement policy, considerations that determine shard placement are:

- Separation of master and replica shards
- Available persistence and Auto Tiering storage
- [Rack-zone awareness]({{< relref "/operate/rs/clusters/configure/rack-zone-awareness" >}})
- Memory available to host the database when fully populated

The shard placement policies are:

- `dense` - Place as many shards as possible on the smallest number of nodes to reduce the latency between the proxy and the database shards;
    Recommended for Redis on RAM databases to optimize memory resources
- `sparse` - Spread the shards across as many nodes in the cluster as possible to spread the traffic across cluster nodes;
    Recommended for databases with Auto Tiering enabled to optimize disk resources

When you create a Redis Software cluster, the default shard placement policy (`dense`) is assigned to all databases that you create on the cluster.

You can:

- Change the default shard placement policy for the cluster to `sparse` so that the cluster applies that policy to all databases that you create
- Change the shard placement policy for each database after the database is created