Resilience Architecture — Azure Solutions Architect (AZ-305)
Failure Scope and Recovery Objective Across HA and DR Tiers
Azure Load Balancer distributes traffic across healthy instances within a region. It does not route across regions and provides no protection against a regional outage. Traffic Manager routes at the DNS level across regions, with propagation latency measured in seconds to minutes. Cosmos DB multi-region active-active writes eliminate data loss for database state at global scale. Blob Storage geo-redundancy replicates objects asynchronously, which means an RPO greater than zero for the most recent writes. Each service addresses a different failure scope: intra-region health, cross-region routing, data replication, and storage redundancy are separate concerns that require separate answers.
What This Pattern Tests
Resilience questions test whether you match the availability design to the stated SLA. Over-designing wastes money (multi-region for a 99.9% target). Under-designing risks downtime (single-AZ for a 99.99% target). The exam penalizes both.
Decision Axis
Stated SLA determines resilience architecture. Design to the requirement, not to the maximum.
Associated Traps
More Top Traps on This Exam
Decision Rules
Whether a sub-one-hour RTO for region-level VM failure requires continuous replication with automated failover (Azure Site Recovery) or can be satisfied by periodic backup-restore (Azure Backup) at lower apparent cost.
Whether the 15-minute RPO can be satisfied by scheduled backup or export cycles, or whether it mandates continuous replication via managed services; the answer also determines whether custom orchestration is justified or whether it introduces failure-path complexity that jeopardizes the 1-hour RTO.
When RTO ≤ 15 minutes is stated for IaaS workloads, backup-restore is disqualified regardless of whether backup frequency can satisfy the RPO; continuous replication with orchestrated failover via Azure Site Recovery is the minimum viable tier.
Domain Coverage
Difficulty Breakdown