RDS Checkpoint and CPU Util sudden spike

Hello.

Checkpoint lag: from100-140 -> 600 CPU Utilization: from 10% -> 30-50%

Is it under load for a long time?
If it's about 1 to 2 hours, I don't think there will be any problem with this kind of load without upgrading the specs.
Also, since it is a database, I recommend checking the memory usage rate as well.
If you enable extended monitoring of RDS, you can see the memory usage rate.
https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_Monitoring.OS.Enabling.html