- A
Configure slow start on the target group
Why wrong: Slow start ramps up traffic to new instances gradually, but does not affect the distribution of existing traffic across instances.
- B
Increase the deregistration delay on the target group
Why wrong: Deregistration delay controls how long in-flight requests are allowed to complete before an instance is deregistered. It does not affect traffic distribution.
- C
Enable sticky sessions (session affinity) on the target group
Why wrong: Stickiness ties a user's session to a specific instance, which can actually cause uneven load if one instance gets more sticky sessions. It does not help balance distribution.
- D
Verify that cross-zone load balancing is enabled on the ALB
Cross-zone load balancing distributes traffic evenly across all instances in all enabled AZs. If disabled, each ALB node only sends traffic to instances in its own AZ, causing uneven distribution.
Quick Answer
The answer is to verify that cross-zone load balancing is enabled on the ALB. When cross-zone load balancing is disabled, each ALB node distributes traffic only to instances within its own Availability Zone, which directly causes uneven distribution if instance counts or capacities vary across zones—a classic source of intermittent high latency. On the AWS Certified SAP on AWS Specialty PAS-C01 exam, this scenario tests your understanding of how ALB node behavior differs from Network Load Balancers, which require explicit enabling; a common trap is assuming ALB default settings are always optimal, but cross-zone load balancing is enabled by default for ALBs, so if it’s been inadvertently disabled, traffic skews immediately. Remember the mnemonic: “ALB Always Loads Balanced” by default, so if traffic is uneven, check that cross-zone hasn’t been toggled off.
PAS-C01 Technology Practice Question
This PAS-C01 practice question tests your understanding of technology. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company runs a critical web application on EC2 instances behind an Application Load Balancer (ALB). The application experiences intermittent high latency, and the operations team suspects that the load balancer is not distributing traffic evenly. Which configuration should the team check to confirm or rule out uneven traffic distribution?
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
Verify that cross-zone load balancing is enabled on the ALB
Uneven traffic distribution across EC2 instances behind an ALB is most commonly caused by cross-zone load balancing being disabled. By default, ALBs have cross-zone load balancing enabled, which distributes traffic evenly across all registered instances in all enabled Availability Zones. If it is disabled, each ALB node distributes traffic only to instances in its own Availability Zone, leading to imbalances when instance counts or capacities differ across zones. Verifying this setting directly addresses the suspected uneven distribution.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure slow start on the target group
Why it's wrong here
Slow start ramps up traffic to new instances gradually, but does not affect the distribution of existing traffic across instances.
- ✗
Increase the deregistration delay on the target group
Why it's wrong here
Deregistration delay controls how long in-flight requests are allowed to complete before an instance is deregistered. It does not affect traffic distribution.
- ✗
Enable sticky sessions (session affinity) on the target group
Why it's wrong here
Stickiness ties a user's session to a specific instance, which can actually cause uneven load if one instance gets more sticky sessions. It does not help balance distribution.
- ✓
Verify that cross-zone load balancing is enabled on the ALB
Why this is correct
Cross-zone load balancing distributes traffic evenly across all instances in all enabled AZs. If disabled, each ALB node only sends traffic to instances in its own AZ, causing uneven distribution.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse uneven distribution with session affinity (sticky sessions) or connection draining, but the root cause is typically the cross-zone load balancing setting, which directly controls whether traffic is balanced across all targets or confined to each Availability Zone.
Detailed technical explanation
How to think about this question
Cross-zone load balancing on an ALB is controlled by a target group attribute (load_balancing.cross_zone.enabled) and defaults to true for ALBs. When disabled, each ALB node in a given Availability Zone distributes traffic only to targets within that same zone, so if one zone has 2 instances and another has 5, the 2-instance zone receives roughly 50% of the traffic (since ALB nodes share traffic equally), causing overload. This behavior is distinct from Network Load Balancers, where cross-zone load balancing is disabled by default and must be explicitly enabled.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this PAS-C01 question test?
Technology — This question tests Technology — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Verify that cross-zone load balancing is enabled on the ALB — Uneven traffic distribution across EC2 instances behind an ALB is most commonly caused by cross-zone load balancing being disabled. By default, ALBs have cross-zone load balancing enabled, which distributes traffic evenly across all registered instances in all enabled Availability Zones. If it is disabled, each ALB node distributes traffic only to instances in its own Availability Zone, leading to imbalances when instance counts or capacities differ across zones. Verifying this setting directly addresses the suspected uneven distribution.
What should I do if I get this PAS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This PAS-C01 practice question is part of Courseiva's free Amazon Web Services 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 PAS-C01 exam.
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