PAS-C01 Sticky sessions Practice Question
A company is migrating a multi-tier web application to AWS. The web tier uses sticky sessions. The application tier uses a shared session store. Which architecture ensures high availability and scalability?
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 an Application Load Balancer with sticky sessions and Amazon ElastiCache for session storage.
An Application Load Balancer (ALB) supports sticky sessions, and Amazon ElastiCache provides a scalable, low-latency, distributed session store that is shared across instances, ensuring high availability and scalability. Option A is incorrect because storing sessions on each EC2 instance does not provide a shared session store; if an instance fails, its sessions are lost. Option B is incorrect because while the Classic Load Balancer supports sticky sessions and RDS can be used as a session store, RDS is not optimized for high-throughput session data and the Classic Load Balancer lacks advanced features like path-based routing and is considered legacy. Option D is incorrect because Amazon CloudFront is a content delivery network (CDN) and is not designed for session storage; S3 is object storage with higher latency, making it unsuitable for real-time session data.
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 an Application Load Balancer with sticky sessions enabled, and store sessions on each EC2 instance.
Why it's wrong here
Incorrect. Storing sessions on each EC2 instance lacks a shared session store, so if an instance fails, sessions are lost. This does not provide high availability.
- ✗
Use a Classic Load Balancer with sticky sessions and store sessions in RDS.
Why it's wrong here
Incorrect. A Classic Load Balancer supports sticky sessions but lacks advanced features. Storing sessions in RDS can cause database bottlenecks and latency, not optimal for a distributed session store.
- ✓
Use an Application Load Balancer with sticky sessions and Amazon ElastiCache for session storage.
Why this is correct
Correct. The Application Load Balancer provides sticky sessions. Amazon ElastiCache is a distributed in-memory cache ideal for a shared session store, supporting high availability and scalability.
- ✗
Use Amazon CloudFront with origin failover and store sessions in S3.
Why it's wrong here
Incorrect. CloudFront is a content delivery network, not a load balancer. S3 is object storage with eventual consistency, not suitable for fast session storage.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
Go deeper
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.