Cacheing and Elasticache

Question 1

What is Elasticache?

Answer 1

Elasticache is a web service that makes it easy to deploy, operate, and scale an in-memory cache in the cloud.

Question 2

What is the benefit of using Elasticache (and caches in general)?

Answer 2

• Elasticached is used to speed up performance of existing databases
• frequent identical queries
• Elasticache improves the performance of web applications by allowing you to retrieve information from fast, managed in-memory caches, instead of relying entirely on slower, disk-based databases.

Question 3

What are the two types of open-source in-memory caching engines that Elasticache supports?

Answer 3

• Memcached
• Redis

Question 4

What is the use case for Elasticache?

Answer 4

Use Elasticache to increase DB and web application performance

Question 5

Does memcached support Multi-AZ?

Answer 5

No

Question 6

Does memcached support Backup and Restore?

Answer 6

No

Question 7

Does memcached support multi-threaded performance?

Answer 7

Yes

Question 8

Does redis support multi-threaded performance?

Answer 8

No

Question 9

Does redis support Multi-AZ?

Answer 9

Yes

Question 10

Does Redis support Backup and Restore?

Answer 10

Yes

Question 11

What concerns need to be balanced when cacheing on AWS?

Answer 11

Cacheing is a balancing act between up-to-date information and latency

Question 12

What are the services on AWS that use cacheing?

Answer 12

• CloudFront
• API Gateway
• Elasticache (memchached and redis)
• DynamoDB Accelerator (DAX)

Question 13

Can Elasticache be used for Pub/Sub type systems?

Answer 13

Yes

Question 14

What are the two types of caches in computer science, and how do they differ?

Answer 14

Lazy Loading cache:
* Only update cache on cache miss
* Higher read performance
* Eventual Consistency

Write-Through cache:
* Update cache on every write
* Lower per-write performance
* Strong consistency

Question 15

What is the retrieval latency for Elasticache?

Answer 15

Sub-millisecond

DynamoDB is only single-digit millisecond