DOP-C02 Resilient Cloud Solutions Practice Question
A company runs a stateful web application on Amazon EC2 instances behind an Application Load Balancer (ALB). The application stores session data in local instance memory. To improve resiliency, the company wants to make the application stateless and distribute the load across multiple Availability Zones. Which THREE actions should the company take? (Choose three.)
⚠ Common exam trap
DOP-C02 often tests the misconception that enabling sticky sessions improves resiliency — in fact, session affinity is the anti-pattern that statelessness is designed to eliminate.
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 ALB to distribute traffic across EC2 instances in multiple Availability Zones.
Option C is correct because an ALB is a regional load balancer that can register targets in multiple Availability Zones, so configuring it to distribute traffic across EC2 instances in several AZs removes the single-AZ failure point and improves resiliency. Option D is correct because moving session data out of local instance memory into an Amazon ElastiCache cluster (e.g., Redis or Memcached) externalizes session state, allowing any instance in any AZ to serve any request and making the application stateless. Option E is correct because Amazon DynamoDB is a fully managed, multi-AZ, highly durable key-value store that can also hold session state externally, achieving the same stateless design without relying on instance memory. Option A is not appropriate because sticky sessions keep a user bound to a single instance and actually perpetuate statefulness rather than eliminate it. Option B is not appropriate because replacing the ALB with an NLB does not address session state at all and an NLB lacks the HTTP/HTTPS layer-7 routing features typically used by web 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.
- ✗
Enable sticky sessions (session affinity) on the ALB.
Why it's wrong here
Sticky sessions bind each client to one EC2 instance, so session data stays in that instance's memory and is lost if it fails; this directly contradicts the stateless goal. Session affinity is used when an application cannot externalise state and must keep a user on one backend.
- ✗
Replace the ALB with a Network Load Balancer (NLB) to improve performance.
Why it's wrong here
An NLB is not required for this use case and does not provide HTTP-level features.
- ✓
Configure the ALB to distribute traffic across EC2 instances in multiple Availability Zones.
Why this is correct
Distributing traffic across multiple Availability Zones directly satisfies the resiliency and load-spreading requirement. The ALB already operates at the regional level, so enabling cross-AZ distribution removes the single-AZ failure domain, ensuring instances in surviving zones continue serving requests when one zone becomes unavailable.
- ✓
Implement an Amazon ElastiCache cluster to store session data externally.
Why this is correct
Storing sessions in ElastiCache removes the local-memory dependency that prevents statelessness, so any instance in any Availability Zone can serve any request. This directly satisfies the stem's requirement to make the application stateless and distribute load across multiple Availability Zones behind the ALB.
- ✓
Use Amazon DynamoDB to store session state.
Why this is correct
Storing session state in DynamoDB removes it from instance memory, so any EC2 instance in any Availability Zone can serve any request. This externalises state, directly satisfying the requirement to make the application stateless for multi-AZ distribution.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
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.