Zero-trust workload identity

Design a zero-trust workload-identity and secrets-distribution system so that 50K microservice instances can authenticate to each other and obtain short-lived credentials (DB passwords, API keys, mTLS certs) with no hardcoded long-lived secrets anywhere. Scale: 500K identity/credential requests/s, certs/secrets must rotate automatically (minutes-to-hours TTL), and a compromised service must not be able to impersonate another. Threat model: secrets leaking in images/env vars/logs, a compromised node, and lateral movement between services. Cover how a workload bootstraps its identity, the cert/secret issuance flow, rotation, and the trust root.