Key management service

Design a key-management service (KMS) for a cloud platform that provides encryption keys to thousands of internal services and customer-managed-key (BYOK) tenants for encrypting data at rest. It must do envelope encryption at 200k cryptographic ops/sec with p99 under 10ms, support customer-controlled key rotation and revocation (a customer revoking their key must render their data unreadable), and keep root key material inside HSMs. Cover the key hierarchy, envelope encryption, rotation, and the BYOK trust/revocation model.