Enterprise High Availability

Purpose

Design and operate systems that hold availability targets from 95% to 99.999% across the full stack: database replica + slave topology, load balancer health contracts, zero-downtime application version rollout, schema/data sync during migration, and quorum-based failover. Applies equally to a solo-built enterprise SaaS and a 10k-node Fortune-500 platform — only the budget, redundancy factor, and automation depth change.

Agent Protocol

Trigger

Exact user phrases: "high availability", "HA", "99.9", "99.99", "99.999", "five nines", "four nines", "three nines", "uptime target", "replica", "read replica", "slave db", "standby", "load balancer", "LB", "HAProxy", "Nginx LB", "ALB", "NLB", "Envoy", "blue-green", "canary", "rolling update", "zero downtime", "version sync", "schema migration", "data sync", "backfill", "dual write", "expand contract", "failover", "quorum", "split brain", "RPO", "RTO", "active-active", "active-passive", "multi-AZ", "multi-region".