SOA-C02 Networking and Content Delivery Practice Question

A company is designing a highly available architecture for a web application using an Application Load Balancer (ALB) across multiple Availability Zones. Which configuration ensures that traffic is distributed evenly across all healthy targets?

⚠ Common exam trap

It's easy for candidates to confuse cross-zone load balancing with sticky sessions or connection draining, assuming that session affinity or graceful termination will improve distribution, when in fact only cross-zone load balancing ensures even traffic spread across all healthy targets.

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

✓

Enable cross-zone load balancing on the ALB

Cross-zone load balancing enables the ALB to distribute incoming traffic evenly across all healthy targets in all enabled Availability Zones, rather than sending traffic only to targets within the same zone as the requesting client. By default, ALBs distribute traffic equally across zones first, then round-robin within each zone, which can lead to uneven load if target counts differ per zone. Enabling cross-zone load balancing overrides this behavior, ensuring each healthy target receives an equal share of requests regardless of its zone.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✓
Enable cross-zone load balancing on the ALB
Why this is correct
Enabling cross-zone load balancing on the ALB allows the load balancer to distribute incoming traffic evenly across all registered targets in all enabled Availability Zones, rather than confining traffic to targets within the same AZ. This is the correct approach because it ensures optimal resource utilization and fault tolerance, especially when workloads or target capacities vary across AZs. Without this feature, each AZ would receive an equal share of traffic, but targets within a less capable AZ could become overwhelmed.
✗
Configure sticky sessions (session affinity) on the target group
Why it's wrong here
Configuring sticky sessions (session affinity) on the target group directs all requests from a given client to the same target for the duration of a cookie-based session. While this is useful for stateful applications, it does not promote even distribution across Availability Zones; in fact, it can cause skewed load because long-lived or high-volume sessions remain pinned to a single target. Uneven distribution across AZs would persist or worsen, so this does not satisfy the high availability or load distribution requirement.
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Use a Network Load Balancer with path-based routing
Why it's wrong here
Using a Network Load Balancer with path-based routing is not a valid solution because NLB operates at Layer 4 (TCP/UDP) and does not support path-based routing, which is an Application Load Balancer feature. Path-based routing requires HTTP/HTTPS protocol awareness and host or path conditions, which ALB provides. Therefore, an NLB cannot fulfill the requirement, and this would not improve even load distribution across AZs.
✗
Enable connection draining on the target group
Why it's wrong here
Enabling connection draining on the target group (also known as deregistration delay) controls how long the ALB waits for in-flight requests to complete before an instance is deregistered or fails health checks. It is a lifecycle management feature that helps maintain session continuity during zero-downtime deployments, but it does not affect the algorithm or distribution of traffic among healthy targets. It neither balances load across AZs nor addresses uneven utilization, so it is not relevant to the high availability requirement.

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SOA-C02 Networking and Content Delivery Practice Question

Why each option matters

Option-by-option breakdown

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