Quick Answer
Amazon ElastiCache for Redis is the correct choice for serverless session state storage because it delivers the sub-millisecond latency required for real-time session management in a Lambda and API Gateway architecture. Unlike DynamoDB, which is optimized for persistence and throughput, Redis provides an in-memory key-value store with built-in TTL expiration, automatically removing stale sessions without additional cleanup logic. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your ability to distinguish between stateful caching needs and durable database requirements—a common trap is selecting DynamoDB for session data, but the exam emphasizes that session state demands the fastest possible read/write performance, not strong consistency or complex queries. Remember that serverless applications are stateless by design, so offloading session state to a dedicated caching layer like ElastiCache for Redis is the architecturally correct pattern. Memory tip: think “Redis for rapid reads, DynamoDB for durable deeds.”
This SAP-C02 practice question tests your understanding of design for new solutions. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
A company is designing a serverless application using AWS Lambda for business logic and Amazon API Gateway for REST APIs. The application needs to store and retrieve user session data. Which service should they use for session state?
Amazon ElastiCache for Redis
Redis is a common choice for session state.
Amazon RDS for MySQL
Why wrong: RDS is not ideal for session state.
Amazon DynamoDB
Why wrong: DynamoDB can be used but is not the best for session state.
Amazon S3
Why wrong: S3 is not designed for low-latency session state.
Answer choices
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 the correct choice for storing user session state in a serverless application because it provides an in-memory data store with sub-millisecond latency, which is ideal for session management where fast reads and writes are critical. Redis supports key-value structures with TTL (time-to-live) expiration, allowing automatic cleanup of stale sessions, and integrates seamlessly with Lambda and API Gateway via the ElastiCache client SDK.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Amazon ElastiCache for Redis
Why this is correct
Redis is a common choice for session state.
Related concept
Read the scenario before looking for a memorised answer.
Amazon RDS for MySQL
Why it's wrong here
RDS is not ideal for session state.
Amazon DynamoDB
Why it's wrong here
DynamoDB can be used but is not the best for session state.
Amazon S3
Why it's wrong here
S3 is not designed for low-latency session state.
Common exam traps
The trap here is that candidates often choose DynamoDB because it is a serverless, managed NoSQL database commonly used with Lambda, but they overlook the specific requirement for session state, which demands in-memory performance and TTL-based expiry that ElastiCache for Redis provides natively.
Detailed technical explanation
Under the hood, ElastiCache for Redis uses a single-threaded event loop with non-blocking I/O, enabling it to handle tens of thousands of operations per second with consistent single-digit millisecond latency. A common real-world scenario is a gaming leaderboard or shopping cart session where TTL-based expiry automatically removes stale data, and Redis's Sorted Sets or Hashes can store complex session attributes without schema changes. The key distinction is that session state is transient and requires fast access, which aligns with Redis's in-memory architecture, whereas DynamoDB's auto-scaling and replication are better suited for durable, long-lived application data.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
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FAQ
Design for New Solutions — This question tests Design for New Solutions — Read the scenario before looking for a memorised answer..
The correct answer is: Amazon ElastiCache for Redis — Amazon ElastiCache for Redis is the correct choice for storing user session state in a serverless application because it provides an in-memory data store with sub-millisecond latency, which is ideal for session management where fast reads and writes are critical. Redis supports key-value structures with TTL (time-to-live) expiration, allowing automatic cleanup of stale sessions, and integrates seamlessly with Lambda and API Gateway via the ElastiCache client SDK.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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.
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