Multi-Tier DR Design: AKS, App Service, SQL Database Failover
Contoso Ltd. is a global e-commerce company running its online store on Azure. The application consists of: - Frontend: Azure App Service (Windows) in West US. - Backend: Azure Kubernetes Service (AKS) cluster in West US. - Database: Azure SQL Database (General Purpose, S2) in West US. - Cache: Azure Cache for Redis (Standard C1) in West US. - Storage: Azure Blob Storage (LRS) for product images.
Business continuity requirements: - RPO: 5 minutes for the database. - RTO: 1 hour for the entire application. - The solution must survive a complete West US region outage. - Budget is limited; minimize additional costs.
What should you recommend as the primary DR strategy?
Quick Answer
The correct primary DR strategy is deploying a secondary region with a passive AKS cluster, a standby App Service plan, and an Azure SQL Database auto-failover group using active geo-replication. This meets the 5-minute RPO because auto-failover groups support synchronous data replication to a paired region, ensuring near-zero data loss, while the pre-provisioned compute resources in the secondary region allow the entire application to fail over within the 1-hour RTO. On the AZ-305 exam, this scenario tests your ability to balance cost and resilience for multi-tier disaster recovery design—the key trap is assuming Azure Site Recovery is needed for everything, but it’s overkill and expensive here; instead, native platform features like Traffic Manager for frontend routing, geo-replication for Redis, and GRS for Blob Storage handle each tier efficiently. Remember the mnemonic “PASS the DR” for paired region, auto-failover, standby compute, and storage redundancy.
⚠ Common exam trap
Many candidates choose zone-redundant options (Option C) thinking they provide regional resilience, but they only protect against zone failures within a region, not a complete region outage, which is explicitly required in the question.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deploy a secondary region (East US) with a passive AKS cluster (minimal node count), a standby App Service plan (same tier), and a secondary Azure SQL Database in an auto-failover group. Use Azure Traffic Manager for frontend and configure Azure Cache for Redis with geo-replication. For Blob Storage, enable geo-redundant storage (GRS).
It meets the RPO of 5 minutes for the database using an auto-failover group with a secondary Azure SQL Database in East US, which provides continuous data synchronization with minimal data loss. The passive AKS cluster (minimal node count) and standby App Service plan minimize costs while ensuring RTO of 1 hour by allowing rapid scaling during failover. Azure Traffic Manager routes frontend traffic to the secondary region, and geo-replication for Redis Cache and GRS for Blob Storage provide data durability across regions, satisfying the requirement to survive a complete West US region outage.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Deploy a secondary region (East US) with a passive AKS cluster (minimal node count), a standby App Service plan (same tier), and a secondary Azure SQL Database in an auto-failover group. Use Azure Traffic Manager for frontend and configure Azure Cache for Redis with geo-replication. For Blob Storage, enable geo-redundant storage (GRS).
Why this is correct
This meets the RPO/RTO with minimal cost by using a passive standby.
- ✗
Use Azure Backup for the database with 5-minute log backup frequency. For the app, use Azure App Service backup with frequency to a secondary region. For AKS, back up persistent volumes using Azure Backup. Restore everything in a secondary region during disaster.
Why it's wrong here
Backup cannot meet 1-hour RTO because restore takes time.
- ✗
Deploy the entire application across two Azure Availability Zones within West US. Use zone-redundant storage for blobs, zone-redundant App Service plan, and zone-redundant AKS. For SQL Database, use a zone-redundant configuration. For Redis, use Enterprise tier with zone redundancy.
Why it's wrong here
Availability Zones do not protect against a regional outage.
- ✗
Use Azure Site Recovery to replicate all VMs (including AKS nodes) to a secondary region. For the database, use Azure SQL Database active geo-replication. For Azure Cache for Redis, replicate data via geo-replication. Use Azure Traffic Manager for frontend traffic routing.
Why it's wrong here
ASR for AKS is not supported; also potentially more expensive.
Quick reference
Azure Blob Storage Tier Comparison
| Tier | Storage Cost | Retrieval Cost | Latency | Use Case |
|---|---|---|---|---|
| Hot | Highest | Lowest | Immediate | Active data, frequent reads |
| Cool | Lower | Higher | Immediate | Data accessed < once / month |
| Cold | Lower still | Higher | Immediate | Data accessed < once / quarter |
| Archive | Lowest | Highest + rehydration delay | Hours | Long-term compliance retention |
Go deeper
Related to this question
Learn chapter
Designing Azure Storage Solutions
Key term
BIA and RPO RTO Design
Business Impact Analysis and the design of Recovery Point Objective and Recovery Time Objective define how much data loss and downtime a business can tolerate after an IT failure, guiding the architecture of backup and disaster recovery systems.
Key term
Azure Site Recovery
Azure Site Recovery is a Microsoft Azure service that keeps your business applications and data running by automatically replicating them to a secondary location and failing over if the primary site goes down.
About these practice questions
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Same concept, more angles
1 more way this is tested on AZ-305
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Contoso is a global e-commerce company that runs its platform on Azure Kubernetes Service (AKS) with Istio service mesh. The application uses Azure Cosmos DB (API for MongoDB) with multi-region writes enabled. The platform also uses Azure Cache for Redis Enterprise for session caching. The business requires a Recovery Time Objective (RTO) of 30 seconds and a Recovery Point Objective (RPO) of 0 for all tiers. You need to design a disaster recovery solution that meets these requirements with high availability. What should you recommend?
hard- A.Deploy AKS in two regions with Azure Traffic Manager. Use Azure Cosmos DB with multi-region writes. Use Azure Cache for Redis Enterprise with active geo-replication.
- B.Deploy AKS in two regions with Azure Front Door. Use Azure Cosmos DB with a single write region and auto-failover. Use Azure Cache for Redis Standard with geo-replication.
- ✓ C.Deploy AKS in two regions with Azure Front Door. Use Azure Cosmos DB with multi-region writes. Use Azure Cache for Redis Enterprise with active geo-replication.
- D.Use Azure SQL Database with auto-failover groups for the database tier. Deploy AKS in two regions with Azure Front Door. Use Azure Cache for Redis Enterprise with active geo-replication.
Why C: It meets the RTO of 30 seconds and RPO of 0 by using Azure Front Door for global load balancing with health probes, Azure Cosmos DB with multi-region writes for zero data loss (RPO=0) and instant failover, and Azure Cache for Redis Enterprise with active geo-replication to provide a writable cache in both regions with sub-30-second failover. This combination ensures that all tiers can fail over independently and instantly without data loss.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-305 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-305 exam.