DOP-C02 Resilient Cloud Solutions Practice Question
A company's application runs on EC2 instances in a single Availability Zone. The operations team wants to improve resilience without redesigning the application. Which action is the MOST effective?
⚠ Common exam trap
Watch out — candidates often confuse instance-level recovery (Auto Recovery) with infrastructure-level resilience (multi-AZ deployment), mistakenly thinking that restarting a failed instance in the same AZ provides sufficient protection against the most common cause of downtime—an AZ outage.
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
✓
Deploy EC2 instances across multiple Availability Zones using an Auto Scaling group.
Deploying EC2 instances across multiple Availability Zones (AZs) using an Auto Scaling group is the most effective action because it eliminates the single point of failure at the AZ level. If one AZ experiences an outage, the Auto Scaling group automatically launches replacement instances in the remaining healthy AZs, ensuring application availability without requiring any application-level changes. This directly addresses the goal of improving resilience by leveraging AWS's fault-isolated infrastructure.
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 a larger instance type to handle more traffic.
Why it's wrong here
Scaling up to a larger instance type increases the CPU, memory, and network capacity available to handle higher traffic, but it does not change the fact that the instance is pinned to a single Availability Zone. If that AZ experiences an outage, the instance remains inaccessible regardless of its size. This is a capacity optimization strategy, not a high-availability strategy, so it fails to address the application's resilience to AZ failure.
- ✗
Enable EC2 Auto Recovery to automatically restart the instance if it fails.
Why it's wrong here
EC2 Auto Recovery detects an impaired instance due to underlying hardware failure and automatically restarts it on a new healthy host, but that host is still within the same Availability Zone. The recovery process preserves the instance ID, private IP, and Elastic IPs, but it cannot migrate the instance to a different AZ. Therefore, if the entire AZ fails, Auto Recovery provides no benefit because the instance is still isolated in the failed AZ.
- ✓
Deploy EC2 instances across multiple Availability Zones using an Auto Scaling group.
Why this is correct
Deploying EC2 instances across multiple Availability Zones with an Auto Scaling group is the standard pattern for high availability. If one AZ becomes unavailable, the load balancer routes traffic to instances in the remaining healthy AZs, and the Auto Scaling group maintains instance count across AZs to replace any that are terminated. This eliminates the single-AZ point of failure and ensures application availability during an AZ outage.
- ✗
Place the instance in a placement group to ensure low latency.
Why it's wrong here
A placement group is designed to reduce network latency and maximize throughput by placing instances in the same rack or within a single Availability Zone. This actually concentrates all instances in one failure domain, so an AZ outage would take down every instance in the placement group. Placement groups target performance optimization for tightly coupled workloads, not resilience, making them irrelevant for protecting against AZ failure.
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Same concept, more angles
1 more way this is tested on DOP-C02
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company has a stateless web application on EC2 instances behind an ALB. They want to ensure that if an entire Availability Zone fails, the application remains available with minimal impact. Which architecture best meets this requirement?
hard- A.Use a global secondary index in DynamoDB to replicate data across regions
- B.Deploy EC2 instances in two AZs but use a single-AZ ALB
- ✓ C.Deploy the application in two AZs with an Auto Scaling group and an ALB that is enabled for multiple AZs
- D.Deploy the application in a single AZ with an Auto Scaling group that launches instances in the same AZ
Why C: Deploying EC2 instances in two AZs with an Auto Scaling group and a multi-AZ ALB ensures that if one AZ fails, the ALB can route traffic to healthy instances in the other AZ, providing high availability with minimal impact. Option A is incorrect: a global secondary index in DynamoDB is used to improve query performance, not to provide compute-layer high availability; the application is stateless on EC2, so resilience depends on the compute and load balancer layer. Option B is incorrect: although EC2 instances are in two AZs, a single-AZ ALB is a single point of failure; if that AZ fails, the ALB becomes unavailable. Option D is incorrect: deploying in a single AZ creates a single point of failure; Auto Scaling within that AZ cannot recover from an AZ failure.
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.