- A
Use a single subnet for all tasks to simplify networking.
Why wrong: Single subnet creates single point of failure.
- B
Configure the ECS service to place tasks in multiple Availability Zones.
Spreads tasks across AZs for fault tolerance.
- C
Increase the task memory reservation to handle peak load.
Why wrong: Memory increase addresses performance, not resilience.
- D
Implement a circuit breaker pattern for downstream dependencies.
Prevents cascading failures by failing fast.
- E
Use scheduled scaling to adjust task count based on historical patterns.
Why wrong: Scheduled scaling is for predictable traffic, not resilience.
Question 1,224 of 1,750
Two Strategies to Improve ECS Fargate Resilience: Multi-AZ and Circuit Breaker
This DOP-C02 practice question tests your understanding of resilient cloud solutions. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Which TWO strategies can be used to improve the resilience of an application running on Amazon ECS with Fargate? (Select TWO.)
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
✓
Configure the ECS service to place tasks in multiple Availability Zones.
Option B is correct because configuring the ECS service to place tasks in multiple Availability Zones distributes the application across physically separate data centers, so if one AZ fails, the tasks in other AZs continue to run. Option D is correct because implementing a circuit breaker pattern for downstream dependencies prevents cascading failures by detecting faults and failing fast, allowing the system to recover gracefully. Option A is incorrect; using a single subnet for all tasks typically places them in a single Availability Zone, reducing fault tolerance. Option C is incorrect; increasing task memory reservation helps handle peak load but does not improve resilience against failures. Option E is incorrect; scheduled scaling adjusts capacity based on historical patterns and does not handle unexpected spikes or failures.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 single subnet for all tasks to simplify networking.
Why it's wrong here
Single subnet creates single point of failure.
- ✓
Configure the ECS service to place tasks in multiple Availability Zones.
Why this is correct
Spreads tasks across AZs for fault tolerance.
Related concept
CIDR notation defines the prefix length.
- ✗
Increase the task memory reservation to handle peak load.
Why it's wrong here
Memory increase addresses performance, not resilience.
- ✓
Implement a circuit breaker pattern for downstream dependencies.
Why this is correct
Prevents cascading failures by failing fast.
Related concept
CIDR notation defines the prefix length.
- ✗
Use scheduled scaling to adjust task count based on historical patterns.
Why it's wrong here
Scheduled scaling is for predictable traffic, not resilience.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
Visual reference
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DOP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this DOP-C02 question test?
Resilient Cloud Solutions — This question tests Resilient Cloud Solutions — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Configure the ECS service to place tasks in multiple Availability Zones. — Option B is correct because configuring the ECS service to place tasks in multiple Availability Zones distributes the application across physically separate data centers, so if one AZ fails, the tasks in other AZs continue to run. Option D is correct because implementing a circuit breaker pattern for downstream dependencies prevents cascading failures by detecting faults and failing fast, allowing the system to recover gracefully. Option A is incorrect; using a single subnet for all tasks typically places them in a single Availability Zone, reducing fault tolerance. Option C is incorrect; increasing task memory reservation helps handle peak load but does not improve resilience against failures. Option E is incorrect; scheduled scaling adjusts capacity based on historical patterns and does not handle unexpected spikes or failures.
What should I do if I get this DOP-C02 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DOP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Last reviewed: Jun 20, 2026
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