AZ-305 Design infrastructure solutions Practice Question
A company is designing a highly available architecture for a web application on Azure VMs. The solution must protect against both planned and unplanned downtime and provide automatic failover. Which TWO Azure services should the company use together? (Choose two.)
⚠ Common exam trap
Candidates often confuse Azure Site Recovery (a disaster recovery service with RTOs of minutes to hours) with high-availability solutions that provide automatic failover within seconds, leading them to select Site Recovery instead of Availability Zones.
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
✓
Azure Availability Zones
Azure Availability Zones (A) protect against datacenter-level failures by distributing VMs across physically separate zones within a region, each with independent power, cooling, and networking. Azure Load Balancer (D) provides automatic failover by distributing incoming traffic across healthy VMs in a backend pool, using health probes to detect and route away from failed instances. Together, they ensure the application remains available during both planned maintenance and unplanned outages, with the Load Balancer handling traffic redirection and Availability Zones providing infrastructure redundancy.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Azure Availability Zones
Why this is correct
Azure Availability Zones are physically separate datacenters within the same Azure region, each with independent power, cooling, and networking. By placing VM replicas across multiple zones, you ensure that a failure of one entire datacenter does not affect all instances, achieving intra-region high availability. This is the foundational building block for many HA architectures and carries a 99.99% VM SLA when two or more instances are deployed across zones.
- ✗
Azure Site Recovery
Why it's wrong here
Azure Site Recovery is a disaster recovery service that replicates Azure VMs from a primary region to a secondary region and orchestrates failover during a full regional outage. Its purpose is to protect against region-wide loss, not to provide redundancy within the same region; failover involves recovery time objectives and requires a secondary site. Because this question concerns resiliency to a datacenter-level fault within one region, Site Recovery is the wrong choice.
- ✗
Azure Traffic Manager
Why it's wrong here
Azure Traffic Manager operates at the DNS level, directing clients to the nearest or healthiest regional endpoint. It cannot detect the health of individual VMs or route traffic between availability zones within a single region; it only makes a coarse routing decision once per DNS lookup. Therefore, it does not contribute to intra-region high availability and would only be relevant for cross-region failover or geographic load distribution.
- ✓
Azure Load Balancer
Why this is correct
Standard Azure Load Balancer provides Layer 4 load balancing and supports zone-redundant frontends, which can distribute inbound TCP/UDP traffic across virtual machines in different availability zones. It continuously probes backend pool health and removes failed instances, ensuring traffic is only sent to healthy VMs. This makes it a fundamental service for building high availability inside a region, complementing Availability Zones.
- ✗
Azure Application Gateway
Why it's wrong here
Application Gateway is a Layer 7 web traffic load balancer that offers SSL termination, URL-based routing, and a Web Application Firewall, and it can be deployed as zone-redundant. However, for a general high-availability architecture of VM workloads, it is an optional enhancement, not the core HA mechanism; the required redundancy is delivered by Availability Zones and a Layer 4 Load Balancer. Overusing it for simple TCP/UDP health checks adds cost and complexity without improving fault tolerance, so it is not one of the two best choices here.
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