- Complete architecture overview with ASCII diagram
- Database replication configuration and verification
- DNS failover monitor details (systemd service)
- Automatic failover sequence explanation
- Live test results from Nov 25, 2025 (90s detection, 0s downtime)
- Critical operational notes (firewall, ports, health checks)
- Manual failover and secondary update procedures
- Documentation references (DEPLOY_SECONDARY_MANUAL.md, HA_SETUP_ROADMAP.md)
- When making changes guidance for HA environment
Status: PRODUCTION READY ✅
All phases tested and validated with zero-downtime failover/failback
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