Aurora Blue/Green deployments require logical replication to be enabled beforehand

Running create-blue-green-deployment with the default parameter group fails with:

Output

SourceClusterNotSupportedFault: Blue/Green Deployments require a DB cluster
with logical replication enabled. Before you create a Blue/Green Deployment
for a DB cluster, associate the DB cluster with a custom DB cluster parameter
group that enables logical replication.

You need a custom parameter group with the engine-specific setting:

Terminal (PostgreSQL)

aws rds modify-db-cluster-parameter-group \
  --db-cluster-parameter-group-name my-params \
  --parameters "ParameterName=rds.logical_replication,ParameterValue=1,ApplyMethod=pending-reboot"

Terminal (MySQL)

aws rds modify-db-cluster-parameter-group \
  --db-cluster-parameter-group-name my-params \
  --parameters "ParameterName=binlog_format,ParameterValue=ROW,ApplyMethod=pending-reboot"

Since ApplyMethod=pending-reboot, you must reboot all instances after applying the parameter group. Check DBClusterParameterGroupStatus is in-sync via describe-db-clusters. Leaving it at pending-reboot causes the same error when creating the Blue/Green deployment.

See the Aurora Blue/Green in Practice series for the full verification.