AZ-305 Design data storage solutions Practice Question
A company uses Azure Redis Cache to improve the performance of a web application. They need to ensure that cached data survives a failover to a secondary region. Which Azure Redis Cache tier should they choose?
⚠ Common exam trap
Candidates often confuse the Standard tier's in-region replication with cross-region disaster recovery, or they assume the Enterprise tier is always the best choice for high availability without considering the specific failover scenario described.
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
✓
Premium tier
The Premium tier of Azure Redis Cache supports geo-replication, which enables data to be replicated across paired regions. This ensures that cached data survives a failover to a secondary region, meeting the requirement for disaster recovery. The Standard tier only provides replication within a single region, while the Basic tier offers no replication at all.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Standard tier
Why it's wrong here
The Standard tier replicates each cache node to a secondary node in the same Azure region, providing high availability against node failures within that datacenter. However, it does not support cross-region geo-replication, so if an entire region becomes unavailable, you cannot fail over to a geographically distant cache. Since the requirement calls for cross-region data persistence, the Standard tier's single-region replication is insufficient and therefore not the correct choice.
- ✗
Basic tier
Why it's wrong here
The Basic tier runs a single cache node with no replication, meaning there is no automatic failover and any node failure or planned maintenance causes data loss and downtime. It is intended only for development, testing, or non-critical scenarios and has no SLA. This tier cannot satisfy any production-level performance or resilience requirement, especially not cross-region geo-replication, so it is squarely wrong for this use case.
- ✓
Premium tier
Why this is correct
The Premium tier is the appropriate choice because it includes built-in geo-replication, allowing you to link two cache instances in different regions to keep data synchronized and provide failover across regions. It also offers enterprise-grade features such as Redis persistence (RDB/AOF), clustering for scalability, and a 99.99% SLA, directly supporting both performance improvement and durable, geographically resilient caching. This tier meets the requirement without unnecessary architectural complexity, making it the correct answer.
- ✗
Enterprise tier
Why it's wrong here
The Enterprise tier does support geo-replication—indeed it offers active-active geo-replication with conflict resolution and uses Redis Enterprise technology—but it comes with significantly higher cost and additional features such as modules, RediSearch, and multi-write capabilities. For a straightforward requirement to improve performance and maintain cross-region data persistence, those extras and the premium price are unjustified. The Premium tier delivers the necessary geo-replication with lower complexity and cost, so Enterprise is not the most correct answer.
Go deeper
Related to this question
Learn chapter
Disaster Recovery Patterns: Active-Active vs Active-Passive
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.
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