SAP-C02 Design for New Solutions Practice Question
A company is designing a new application that will run on AWS. The application needs to store and retrieve user session data with low latency. The session data is small (less than 1 KB per user) and must be highly available. The company expects up to 10 million active users per day. Which AWS service should be used as the session store?
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
✓
Amazon ElastiCache for Redis
Amazon ElastiCache for Redis is an in-memory data store designed for low-latency access, making it ideal for session storage for millions of users. Option A: DynamoDB has higher latency compared to in-memory stores. Option B: S3 is object storage and not suitable for low-latency session data. Option C: RDS for MySQL is relational and slower for session access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Amazon DynamoDB
Why it's wrong here
Amazon DynamoDB, while offering low-latency access and high scalability for persistent data, is not the optimal choice for ephemeral user session data requiring the absolute lowest latency. Session stores typically benefit from in-memory caching solutions for sub-millisecond response times. However, DynamoDB is a strong candidate for scenarios demanding a highly available, flexible NoSQL database for persistent data, such as user profiles, product catalogues, or application state where data durability is paramount and single-digit millisecond latency is acceptable.
- ✗
Amazon S3
Why it's wrong here
Amazon S3 is an object storage service with higher latency and not designed for frequent small reads/writes required for session data.
- ✗
Amazon RDS for MySQL
Why it's wrong here
Amazon RDS for MySQL is a relational database with higher latency compared to in-memory solutions, making it less optimal for high-throughput session storage.
- ✓
Amazon ElastiCache for Redis
Why this is correct
Amazon ElastiCache for Redis is an in-memory key-value store that provides sub-millisecond latency, making it the best choice for storing user session data for up to 10 million active users.
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 SAP-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 SAP-C02 exam.