It also allows you to prewarm a read replica before sending queries to it. You can also do this by slowly ramping up traffic to it (and may want to do that anyway for other reasons) but depending on the app and query patterns, that by itself may not be enough especially if you are worried about your p99 latencies.
It can also be helpful when you have network attached storage (eg. EBS volume in AWS) since even if it is SSD you still have the network latency for each IO.
Comments
It also allows you to prewarm a read replica before sending queries to it. You can also do this by slowly ramping up traffic to it (and may want to do that anyway for other reasons) but depending on the app and query patterns, that by itself may not be enough especially if you are worried about your p99 latencies.
It can also be helpful when you have network attached storage (eg. EBS volume in AWS) since even if it is SSD you still have the network latency for each IO.