Complete procedures with a way back.

Operate a Keepalived VRRPv3 pair with explicit priority, non-preemptive recovery, bounded health tracking, protocol-aware firewalling, packet evidence, split-brain fencing, and tested failover.

Deploy HAProxy 3.2 LTS as a validated HTTPS load balancer with application-aware health checks, observable backend state, controlled certificate renewal, and zero-downtime reloads.

Deploy two supported Kea 3.0 LTS DHCPv4 peers in hot-standby mode with identical subnet policy, durable independent lease stores, fixed-address reservations, peer-only native HA listeners, automatic takeover guarded against split brain, and a controlled lease resynchronization path.

Deploy three independent Redis Sentinels around a TLS/ACL-protected Redis Open Source 8.8 primary and two replicas, prove quorum versus majority, validate Sentinel-aware clients and test promotion, fencing and backup restore.

Create tested Prometheus 3.13.1 rules and an Alertmanager 0.32.1 HA route tree with stable labels, grouping, deduplication, inhibition, protected secrets and a safe nonpaging test lane.

Build and operate a PostgreSQL 18.4 hot standby with bounded WAL retention, verified lag, explicit fencing, planned promotion, endpoint cutover, and safe rewind or rebuild.

Balance requests across private backends, set explicit connect/read timeouts, use passive health behavior, preserve client context, and rehearse one-node failure.