Does the Optimize Table Operation Lock Tables on an RDS DB Instance?
When the OPTIMIZE TABLE operation is performed on an RDS DB instance, the tables are locked only for a short period of time. During the table locking period, DML operations can be performed but DDL operations cannot. DML will recreate tables, which consumes CPU and disk resources. If there are a large number of concurrent DML, the table locking duration will be longer. Therefore, you are advised to perform the OPTIMIZE TABLE operation during off-peak hours.