# Application Best Practices for ScyllaDB Cloud

These recommendations apply to the applications and keyspace schemas you
build on top of ScyllaDB Cloud. Following them ensures high availability,
consistent performance, and efficient use of your cluster.

## Use NetworkTopology Replication Strategy

`NetworkTopologyStrategy` is the only replication strategy suitable for
production use. It is also the default in ScyllaDB — you do not need to
specify it explicitly when creating a keyspace.

All of the following are valid and equivalent:

```cql
-- Omit replication entirely (defaults to NetworkTopologyStrategy)
CREATE KEYSPACE my_keyspace;

-- Specify the class explicitly
CREATE KEYSPACE my_keyspace WITH replication = {
  'class': 'NetworkTopologyStrategy',
  'replication_factor': 3
};

-- Specify per-DC replication
CREATE KEYSPACE my_keyspace WITH replication = {
  'class': 'NetworkTopologyStrategy',
  '<datacenter_name>': 3
};
```

If you do specify a replication strategy, always use `NetworkTopologyStrategy`.
Never use `SimpleStrategy` in a production environment — it does not account
for Availability Zone placement, does not support Multi-DC configurations, and
cannot be changed later on tablet-based keyspaces.

Learn more: [CREATE KEYSPACE — ScyllaDB Docs](https://docs.scylladb.com/manual/stable/cql/ddl.html#create-keyspace)

## Use the Correct Consistency Level

* For a single-DC cluster, use **Quorum** consistency.
* For a Multi-DC cluster, use **LocalQuorum** consistency.

Using `ONE` or `ANY` reduces durability. Using `ALL` reduces
availability — if any replica is down, the query will fail.

## Match the Replication Factor to Your Cluster

When creating keyspaces, set the Replication Factor (RF) to match the RF
you selected when creating the cluster. A lower RF reduces availability;
a higher RF may place more than one replica in the same Availability Zone,
which is wasteful and provides no additional fault tolerance.