Multi-region architecture trades cost and complexity for latency, availability, disaster tolerance, or residency. Before adding regions, define failure domains, tenant placement, write ownership, consistency, RPO, RTO, failover authority, and failback. AI inputs, retrieval indexes, telemetry, and provider processing must follow the same residency and deletion policy as source data.
For SupportDesk AI, a tenant home region often balances global read/service presence with clear write ownership and residency. Use globally unique IDs, version events, and routing metadata whose failure mode is defined.
If both regions accept conflicting writes after losing coordination, later reconciliation can violate ticket state, idempotency, quotas, and approvals. Promotion needs fencing: old writer credentials or leases are revoked, routing switches after health/replication checks, and clients cannot keep writing to the old primary.
Document source, extracted text, embeddings, prompt context, model processing, logs, and evaluation samples may all be regulated data. Model-provider availability is region-specific and volatile. Routing policy must enforce allowed provider/region and specify a compliant degraded mode. A global cache or vector index can silently break residency.
Run controlled exercises: regional ingress loss, primary database failure, replication lag, object-store unavailability, model region outage, and stale routing. Measure actual RPO/RTO, integrity, queue reconciliation, idempotency, tenant isolation, cost, and failback. Update the runbook from evidence.
Derived AI data multiplies recovery dependencies. Rebuildable vectors need lineage and versioned source; durable approvals and AI-run audit remain protected. Failover cannot silently route private context to a prohibited provider.
Design active-passive for tenant A restricted to one geography and tenant B global with a home region. Simulate 15 minutes of replication lag during provider and database regional failure.
Acceptance criteria: write authority is singular, potential data loss is quantified, prohibited model routing cannot occur, derived indexes reconcile from durable lineage, and failback has a tested sequence.