Caching And Content Delivery Optimization — AWS Solutions Architect (SAA-C03)
What sits upstream of the cache defines which service
"Reduce database read load for repeated queries" points to ElastiCache — Redis for complex data structures, Memcached for simple key-value. "Reduce latency for DynamoDB item reads" points to DAX, not ElastiCache. "Cache static web content for a global audience" points to CloudFront. Candidates apply ElastiCache generically to any caching scenario. The exam distinguishes by what is being cached: relational query results, DynamoDB items, and HTTP objects are handled by different services with different invalidation models and consistency guarantees.
What This Pattern Tests
The exam describes a performance requirement and tests caching layer selection. CloudFront (CDN) caches static content and API responses at edge locations — reduces origin load and latency for geographically distributed users. ElastiCache Redis caches application data (session state, leaderboards, query results) with sub-millisecond reads. DAX sits in front of DynamoDB as a transparent read-through/write-through cache. The trap is using CloudFront to cache highly dynamic, personalized content (low cache hit ratio) or ElastiCache for content that changes every second (cache invalidation overhead exceeds cache benefit).
Decision Axis
Content type and access pattern determine caching layer: static content = CDN, repeated queries = application cache, DynamoDB hot keys = DAX.
Associated Traps
More Top Traps on This Exam
Decision Rules
Select Amazon CloudFront for global read/download distribution because it caches objects at edge PoPs and reduces origin GET load; reject S3 Transfer Acceleration because it accelerates only the upload path and adds no caching or read-side benefit.
Domain Coverage
Difficulty Breakdown