The principles of extreme fault tolerance

This post details the principles of extreme fault tolerance (isolation, redundancy, static stability) and how they are applied to PlanetScale's architecture (control plane, data plane, database clusters) and processes (always failing over, synchronous replication, progressive delivery). It elaborates on specific failure modes and mitigation strategies for instance, zonal, and regional cloud provider failures, as well as PlanetScale-induced failures, emphasizing the role of feature flags and gradual rollouts.