DOP-C02 Resilient Cloud Solutions Practice Question
A company runs a stateless web application on EC2 instances behind an Application Load Balancer. To improve resilience, which configuration should be used for the EC2 instances?
⚠ Common exam trap
Candidates often think scaling vertically (larger instance) or using multiple instances in a single AZ is sufficient, but the DOP-C02 exam specifically tests the requirement for multi-AZ deployment to achieve resilience against AZ failures.
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
✓
Use multiple EC2 instances across two or more Availability Zones
D is correct because deploying multiple EC2 instances across two or more Availability Zones (AZs) ensures high availability and fault tolerance. If one AZ fails, the Application Load Balancer (ALB) automatically routes traffic to healthy instances in other AZs, maintaining service continuity. This aligns with the AWS Well-Architected Framework's resilience best practices for stateless applications.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use one EC2 instance with a larger instance type
Why it's wrong here
A larger instance type increases capacity on a single host but introduces no redundancy; the instance or its Availability Zone failing still causes an outage. Vertical scaling suits workloads constrained by per-instance compute or memory limits. Resilience instead requires multiple instances distributed across Availability Zones behind the load balancer.
- ✗
Use a single, large EC2 instance in one Availability Zone
Why it's wrong here
A single instance in one Availability Zone gives no redundancy: an AZ outage or instance failure takes the application offline entirely, defeating the resilience goal. Single-instance deployments suit development or non-critical workloads where cost outweighs availability. Resilience requires instances spread across multiple Availability Zones behind the load balancer.
- ✗
Use multiple EC2 instances in one Availability Zone with health checks disabled
Why it's wrong here
Multiple instances within one Availability Zone still share that zone's failure domain, so an AZ outage removes all capacity; disabling health checks also prevents the load balancer from routing around failed instances. Health checks exist to detect and replace unhealthy targets. Spreading instances across multiple Availability Zones provides the required resilience.
- ✓
Use multiple EC2 instances across two or more Availability Zones
Why this is correct
Spreading instances across two or more Availability Zones ensures the application survives an AZ outage, since the Application Load Balancer routes to healthy targets in remaining zones. This directly satisfies the resilience requirement for the stateless workload.
Go deeper
Related to this question
About these practice questions
Courseiva writes every DOP-C02 question from scratch — 1,298 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DOP-C02 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 DOP-C02 exam.