# InstanceUpdateBehaviour

The orchestration of updates of multiple instances.

- Source: [`aws-rds/lib/cluster.ts`](https://github.com/aws/aws-cdk/blob/v2.275.0/packages/aws-cdk-lib/aws-rds/lib/cluster.ts#L541)
- Type last changed: v2.32.0 · 14 Jul 2022

## Example

```ts
declare const vpc: ec2.Vpc;
const cluster = new rds.DatabaseCluster(this, 'Database', {
  engine: rds.DatabaseClusterEngine.auroraMysql({ version: rds.AuroraMysqlEngineVersion.VER_3_01_0 }),
  writer: rds.ClusterInstance.provisioned('Instance', {
    instanceType: ec2.InstanceType.of(ec2.InstanceClass.BURSTABLE3, ec2.InstanceSize.SMALL),
  }),
  readers: [rds.ClusterInstance.provisioned('reader')],
  instanceUpdateBehaviour: rds.InstanceUpdateBehaviour.ROLLING, // Optional - defaults to rds.InstanceUpdateBehaviour.BULK
  vpc,
});
```

## Members

| Member | Description |
| --- | --- |
| `BULK` | In a bulk update, all instances of the cluster are updated at the same time. |
| `ROLLING` | In a rolling update, one instance after another is updated. |

## Referenced by

- [`DatabaseClusterFromSnapshotProps`](/v2/docs/aws-cdk-lib.aws_rds.DatabaseClusterFromSnapshotProps).instanceUpdateBehaviour
- [`DatabaseClusterProps`](/v2/docs/aws-cdk-lib.aws_rds.DatabaseClusterProps).instanceUpdateBehaviour