Amazon ElastiCache: In-Memory Caching for Database Query Results
A web application queries a relational database for a product catalogue that changes infrequently but is requested thousands of times per second. Database query latency is becoming a bottleneck. Which AWS service can the company use to cache frequently accessed query results in memory and reduce database load?
Quick Answer
Amazon ElastiCache is the correct choice because it provides an in-memory caching layer for database query results, using Redis or Memcached to store frequently accessed data and dramatically reduce latency for high-throughput read workloads. By caching query results in memory, ElastiCache offloads repeated requests from the relational database, directly addressing the bottleneck of thousands of queries per second on infrequently changing data. On the AWS Certified Cloud Practitioner CLF-C02 exam, this scenario tests your understanding of how in-memory caching improves application performance and reduces database load, often appearing as a contrast to services like Amazon RDS or DynamoDB Accelerator (DAX). A common trap is confusing ElastiCache with a database itself—remember, it is a cache, not a primary data store. Memory tip: think "ElastiCache = Elastic + Cache" to recall it scales in-memory storage for lightning-fast reads.
⚠ Common exam trap
It's easy for candidates to confuse a read replica (Option A) with a caching solution, not realizing that a read replica still executes SQL queries against a relational engine and does not provide the in-memory speed needed for thousands of requests per second.
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
Amazon ElastiCache is the correct choice because it provides an in-memory caching layer (using Redis or Memcached) that can store frequently accessed query results, reducing the need to repeatedly query the relational database. This dramatically lowers latency for high-throughput read workloads (thousands of requests per second) and offloads database pressure, directly addressing the bottleneck described.
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 RDS Read Replica
Why it's wrong here
Read replicas distribute read traffic but still query the database engine. For caching query results that change infrequently, in-memory caching with ElastiCache is significantly faster and reduces database compute costs.
- ✗
Amazon S3
Why it's wrong here
S3 is object storage, not an in-memory cache. While you could store cached data in S3, retrieval latency is much higher than an in-memory cache.
- ✓
Amazon ElastiCache
Why this is correct
ElastiCache provides fully managed in-memory caching with Redis or Memcached. Caching the product catalogue in ElastiCache means most requests never reach the database, dramatically reducing latency and database load.
- ✗
Amazon DynamoDB
Why it's wrong here
DynamoDB provides single-digit millisecond latency but is still a disk-backed database. For reducing relational database query load with sub-millisecond caching, ElastiCache (in-memory) is the appropriate service.
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Same concept, more angles
1 more way this is tested on CLF-C02
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company runs a high-traffic e-commerce application. During peak holiday season, database read performance degrades. They want to offload read traffic from their RDS primary database. What should they implement?
medium- A.RDS Multi-AZ
- ✓ B.RDS Read Replicas
- C.Increase the RDS instance size
- D.Enable RDS Automated Backups
Why B: B is correct because RDS Read Replicas are specifically designed to offload read traffic from the primary database instance. By creating one or more read-only replicas, the application can direct SELECT queries to the replicas, reducing the load on the primary RDS instance and improving overall read performance during peak traffic.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CLF-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 CLF-C02 exam.