The usage of MariaDB RDS suddenly spiked up to 60%.

We have been providing AR web services since March 17th. Normally, the RDS CPU usage was only up to 4-5%, but there was a history of it using up to 60% today, so we are investigating the cause. Currently, RDS is created in a private area, and we understand that it can only be accessed by EC2 created in the same VPC. We checked the access logs of the Ubuntu EC2, but it seems that only two workers accessed the EC2 with their IP addresses. We are wondering if there is any other way to access the private RDS, and if CPU resources can be used like this when automatic RDS backups are performed. The RDS specification is db.m5.large, and MariaDB and the EC2 specification is c5n.2xlarge Ubuntu. Approximately 1 minute later, CloudWatch logs showed [Warning] Aborted connection numbers to db: 'unconnected' user: 'rdsadmin' host: 'localhost' (Got an error reading communication packets).