Report on our investigation of the 2025-10-20 incident in AWS us-east-1

This post details an incident in AWS us-east-1 caused by DNS misconfiguration and subsequent capacity constraints and network instability. It describes two phases: the first impacting the PlanetScale control plane due to upstream AWS service outages (DynamoDB, S3, STS), and the second impacting some database branches due to EC2 instance launch failures and network partitions. The post highlights PlanetScale's resilience through control/data plane isolation and automated failover, but also identifies areas for improvement, including reducing dependencies on SaaS providers and better utilizing AWS availability zones to mitigate network partition failures.