Quick Answer
Amazon ElastiCache for Redis is the correct choice because it provides a fully managed, in-memory data store that delivers sub-millisecond latency, which is essential for session management with low-latency requirements across multiple EC2 instances. Redis excels here by storing session data in memory rather than on disk, allowing any instance to read or write user state instantly, while its built-in TTL (time-to-live) keys automatically expire stale sessions without manual cleanup. On the AWS Certified Database Specialty DBS-C01 exam, this question tests your understanding of when to use in-memory caching versus relational or NoSQL databases for transient, high-speed access patterns—a common trap is choosing DynamoDB for its managed scalability, but DynamoDB’s single-digit millisecond latency cannot match Redis’s sub-millisecond performance for session workloads. Remember the memory tip: “Sessions are fleeting, so Redis is the meeting point for speed and TTL.”
This DBS-C01 practice question tests your understanding of workload-specific database design. 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 needs to store and manage user sessions for a web application. The application runs on multiple EC2 instances, and sessions must be accessible from any instance. The team wants a fully managed, highly available, and low-latency solution. Which AWS service should they use?
Amazon RDS for MySQL
Why wrong: RDS is a relational database with higher latency, not optimal for session storage.
Amazon ElastiCache for Redis
Redis is ideal for session storage with low latency and high availability.
Amazon DynamoDB
Why wrong: DynamoDB can be used but is typically slower than Redis for session management.
Amazon S3
Why wrong: S3 is object storage, not suitable for frequent read/write session data.
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 fully managed, in-memory data store with sub-millisecond latency, making it ideal for storing user session data that must be accessed from any EC2 instance. Redis supports atomic operations and data structures (e.g., TTL-based key expiration) that are well-suited for session management, and its replication and Multi-AZ failover ensure high availability. This meets the requirement for a fully managed, highly available, and low-latency solution without the overhead of managing a database cluster.
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 RDS for MySQL
Why it's wrong here
RDS is a relational database with higher latency, not optimal for session storage.
Amazon ElastiCache for Redis
Why this is correct
Redis is ideal for session storage with low latency and high availability.
Related concept
Read the scenario before looking for a memorised answer.
Amazon DynamoDB
Why it's wrong here
DynamoDB can be used but is typically slower than Redis for session management.
Amazon S3
Why it's wrong here
S3 is object storage, not suitable for frequent read/write session data.
Common exam traps
The trap here is that candidates often choose Amazon DynamoDB because it is fully managed and highly available, but they overlook the specific requirement for 'low-latency' (sub-millisecond) that only an in-memory cache like ElastiCache for Redis can provide, and they miss that DynamoDB's latency is higher due to disk I/O and consistency models.
Detailed technical explanation
Under the hood, ElastiCache for Redis stores session data entirely in RAM, using a single-threaded event loop to process commands like GET, SET, and EXPIRE with O(1) time complexity, ensuring consistent sub-millisecond performance. Redis supports key eviction policies (e.g., LRU) and replication across Availability Zones, so if a primary node fails, a read replica can be promoted automatically, maintaining session availability. In a real-world scenario, a web application with thousands of concurrent users can use Redis to store session tokens as keys and serialized user data as values, with TTLs set to the session timeout, avoiding the need for a separate cleanup process.
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
Workload-Specific Database Design — This question tests Workload-Specific Database Design — 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 fully managed, in-memory data store with sub-millisecond latency, making it ideal for storing user session data that must be accessed from any EC2 instance. Redis supports atomic operations and data structures (e.g., TTL-based key expiration) that are well-suited for session management, and its replication and Multi-AZ failover ensure high availability. This meets the requirement for a fully managed, highly available, and low-latency solution without the overhead of managing a database cluster.
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 DBS-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 DBS-C01 exam.
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