The CPU Utilization is the percent of an instance’s CPU that is being consumed.  CPU Utilization usually correlates with other metrics such as the amount of operations being performed on the database, number of database connections, and slow queries.  Finding the cause of a CPU Utilization change depends on your database engine, underlying schema, and access patterns. Common causes of CPU utilization anomalies include:

    • Read replica being promoted to a writer
    • Restoring from backup
    • Slow queries
    • Increase in number of reads or writes
    • MySQL Sleeping connections


    CPU Credit Balance

    For RDS instances that are of type db.t2 or db.t3, your CPU performance is dependent on your CPU Credit Balance. When CPU usage is low you accumulate CPU credits and when CPU usage exceeds the baseline performance you consume CPU credits. On T2 RDS instances, once you run out of CPU credits your CPU usage will be throttled, resulting in longer read and write times. On T3 RDS instances, unlimited CPU is enabled and you will be charged for CPU credit usage once your balance reaches zero. Blue Matador automatically tracks when your CPU credit balance will reach zero on T2 or T3 instances so you can take action before performance is impacted.

    If your CPU credit balance is consistently low, consider upgrading your RDS instance to a larger burstable size or to a non-burstable instance that will have guaranteed CPU performance at all times.