A Database Specialist is troubleshooting an application connection failure on an Amazon Aurora DB cluster with multiple Aurora Replicas that had been running wi...

A Database Specialist is troubleshooting an application connection failure on an Amazon Aurora DB cluster with multiple Aurora Replicas that had been running with no issues for the past 2 months. The connection failure lasted for 5 minutes and corrected itself after that. The Database Specialist reviewed the AmazonRDS events and determined a failover event occurred at that time. The failover process took around 15 seconds to complete.
What is the MOST likely cause of the 5-minute connection outage?