High Availability and Resilience Design
This topic covers availability zones, availability sets, scale sets, load balancing, database HA, geo-redundant storage, failover, and resilience testing.
How to study for AZ-305
Treat each AZ-305 item as an architecture decision: identify the workload requirement, governance boundary, data shape, recovery objective, and infrastructure tradeoff before choosing.
Core concepts
Concept 1
High Availability and Resilience Design questions test Azure architecture tradeoff decisions rather than isolated service-name recall.
Exam cue: Identify the requirement, workload type, data shape, access boundary, recovery target, and operational ownership model.
Concept 2
The best answer maps business requirements to identity, governance, data, resilience, compute, network, security, cost, and operations constraints.
Exam cue: Choose the Azure design that satisfies the constraint with the least unnecessary operational burden.
Concept 3
Eliminate answers that ignore governance scope, recovery objectives, data durability, private connectivity, security boundaries, or workload fit.
Exam cue: Prefer Well-Architected choices: secure, reliable, cost-aware, observable, governed, and scalable.
Risk pitfalls and guardrails
Choosing a service before identifying the business driver and nonfunctional requirement.
Guardrail: Avoid answers that pick services without checking governance scope, data model, recovery target, migration dependency, or network boundary.
Solving availability while ignoring identity, data protection, compliance, or cost constraints.
Guardrail: Avoid answers that pick services without checking governance scope, data model, recovery target, migration dependency, or network boundary.
Assuming a migration, networking, or storage pattern is correct without checking workload dependencies.
Guardrail: Avoid answers that pick services without checking governance scope, data model, recovery target, migration dependency, or network boundary.
Memory anchors
Availability Zone
An availability zone is a physically separate datacenter location within an Azure region.
Availability Set
An availability set spreads VMs across fault and update domains within a region.
Virtual Machine Scale Set
A virtual machine scale set manages a group of load-balanced VMs with autoscale support.
Zone Redundant Service
A zone-redundant service can continue operating during a zone-level failure when configured.
Load Balancer
Azure Load Balancer distributes layer 4 traffic across healthy backend instances.
Application Gateway
Application Gateway provides layer 7 load balancing, routing, TLS termination, and WAF integration.
Database Failover
Database failover shifts service to a standby or replicated database when the primary is unavailable.
Geo Redundant Storage
Geo-redundant storage replicates data to a secondary region for regional durability.
Health Probe
A health probe determines whether an instance should receive traffic.
Resilience Test
A resilience test validates that the architecture meets availability assumptions.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
You must protect VMs against a single datacenter failure within a region so the application stays available. Which feature fits?
Your design must protect VMs against hardware and maintenance failures within a single datacenter. Which construct fits?
Answer all questions to submit.
Next step personalized recommendations
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Move forward only after this module is stable.
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