Quick Answer
The answer is Amazon ElastiCache for Redis, as it provides a low-latency, in-memory data store purpose-built to store session state shared across Lambda invocations in serverless applications. Unlike DynamoDB, which is disk-based and introduces higher latency for frequent read-write operations, ElastiCache for Redis keeps session data in memory, enabling sub-millisecond response times that are critical for maintaining state across concurrent function executions. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of stateless versus stateful architectures and the trade-offs between managed caching services and database services—a common trap is choosing DynamoDB for its serverless nature, but the exam emphasizes that session state demands the speed of an in-memory cache, not a durable database. Remember the memory tip: “Session state needs speed, not a disk—Redis is the quick fix.”
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 startup is building a serverless application using AWS Lambda. They need to store session state that can be shared across multiple Lambda invocations. Which AWS service should they use?
Amazon ElastiCache for Redis
Provides low-latency in-memory caching for session state.
Amazon S3
Why wrong: S3 has higher latency for session state.
Amazon DynamoDB
Why wrong: DynamoDB is a NoSQL database, but not ideal for low-latency session state compared to ElastiCache.
Amazon CloudFront
Why wrong: CloudFront is a content delivery network.
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 because it provides a low-latency, in-memory data store that can be shared across multiple Lambda invocations. Redis supports data structures like strings, hashes, and lists, making it ideal for storing session state that needs to be accessed and updated quickly by concurrent serverless functions.
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
Provides low-latency in-memory caching for session state.
Related concept
Read the scenario before looking for a memorised answer.
Amazon S3
Why it's wrong here
S3 has higher latency for session state.
Amazon DynamoDB
Why it's wrong here
DynamoDB is a NoSQL database, but not ideal for low-latency session state compared to ElastiCache.
Amazon CloudFront
Why it's wrong here
CloudFront is a content delivery network.
Common exam traps
The trap here is that candidates often choose DynamoDB because it is a common serverless database, but they overlook that the question specifically asks for shared session state across invocations, which demands in-memory caching for performance, not a persistent database.
Detailed technical explanation
ElastiCache for Redis uses an in-memory key-value store with sub-millisecond latency, supporting atomic operations like INCR and EXPIRE for session management. In a serverless architecture, Lambda functions can connect to a Redis cluster via a VPC or using IAM authentication with Redis AUTH, ensuring session data persists across invocations and is shared across concurrent executions. A real-world scenario is a gaming leaderboard where multiple Lambda functions update player scores in Redis, requiring immediate consistency and low latency.
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 because it provides a low-latency, in-memory data store that can be shared across multiple Lambda invocations. Redis supports data structures like strings, hashes, and lists, making it ideal for storing session state that needs to be accessed and updated quickly by concurrent serverless functions.
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 24, 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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