DOP-C02 Question #41: Real Exam Question with Answer & Explanation

Question

You are creating a new API for video game scores. Reads are 100 times more common than writes, and the top 1% of scores are read 100 times more frequently than the rest of the scores. What's the best design for this system, using DynamoDB?

Options

• ADynamoDB table with 100x higher read than write throughput, with CloudFront caching.
• BDynamoDB table with roughly equal read and write throughput, with CloudFront caching.
• CDynamoDB table with 100x higher read than write throughput, with ElastiCache caching.
• DDynamoDB table with roughly equal read and write throughput, with ElastiCache caching.

Explanation

Because the 100x read ratio is mostly driven by a small subset, with caching, only a roughly equal number of reads to writes will miss the cache, since the supermajority will hit the top 1% scores. Knowing we need to set the values roughly equal when using caching, we select AWS ElastiCache, because CloudFront cannot directly cache DynamoDB queries, and ElastiCache is an excellent in-memory cache for database queries, rather than a distributed proxy cache for content delivery. ... One solution would be to cache these reads at the application layer. Caching is a technique that is used in many high-throughput applications, offloading read activity on hot items to the cache rather than to the database. Your application can cache the most popular items in memory, or use a product such as ElastiCache to do the same. GuidelinesForTables.CachePopularItem

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