How do you design for high availability across Azure availability zones and regions?
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of Microsoft Azure conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
Start with RTO and RPO, then choose a topology.
- Within a region, distribute workloads across availability zones, which are physically separate datacentres. Use zone-redundant services: zone-redundant App Service, AKS across zones, zone-redundant storage, and zone-redundant SQL or Cosmos DB.
- Load balancing: Azure Load Balancer for layer 4, and Application Gateway or Front Door for layer 7 and global routing.
- Across regions, use paired regions and Azure Front Door or Traffic Manager with health probes for failover.
- Data: Cosmos DB multi-region writes, Azure SQL auto-failover groups, and geo-redundant storage.
az sql failover-group create -g rg-db --server sql-primary \
--partner-server sql-secondary --name fg-app
Test failover regularly, and watch for split-brain, replication lag, DNS TTL, and cost. Active-active is resilient but complex; active-passive is simpler but slower to recover.
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.