Which approach meets these requirements?
Set the max_connections parameter to 16,000 in the instance-level parameter group.
Modify the client connection timeout to 300 seconds.
Create an Amazon RDS Proxy database proxy and update client connections to point to the proxy endpoint.
Enable the query cache at the instance level.
Explanations:
The max_connections parameter determines the maximum number of concurrent connections allowed to the database instance. It does not directly improve RTO or recovery time after failovers.
Modifying the client connection timeout to 300 seconds will only change how long clients will wait for a response before timing out. It does not address recovery time or failover speed.
Amazon RDS Proxy acts as a highly available intermediary between the application and the Aurora database. It improves the application recovery time after failovers by reducing the time to reconnect to the database and handling connection pooling.
Enabling the query cache at the instance level can improve performance by caching query results, but it does not impact the recovery time after failovers or RTO.
I opine that the answer is:
Create an Amazon RDS Proxy database proxy and update client connections to point to the proxy endpoint.