What could be the reason for this?
When stopping the DB instance, the option to create a snapshot should have been selected.
When stopping the DB instance, the duration for stopping the DB instance should have been selected.
Stopped DB instances will automatically restart if the number of attempted connections exceeds the threshold set.
Stopped DB instances will automatically restart if the instance is not manually started after 7 days.
Explanations:
Selecting the option to create a snapshot is not required to prevent access to the DB instances. Creating a snapshot is a separate task that captures the state of the database, but does not affect the ability to stop or prevent access to the DB instances.
The duration for stopping the DB instance is not a relevant setting for preventing access. Stopping a DB instance doesn’t require specifying a duration; the DB instance can be stopped indefinitely until manually started.
Stopped DB instances will not automatically restart due to attempted connections. Once stopped, a DB instance remains stopped until manually started, regardless of connection attempts.
Stopped DB instances are automatically restarted by AWS after 7 days if they are not manually restarted. This is a default behavior to ensure that DB instances are not left in a stopped state indefinitely.
I appraise that the answer is:
Stopped DB instances will automatically restart if the instance is not manually started after 7 days.