48. Elasticache

i. Elasticache is a web service that makes it easy to deploy, operate and scale an in-memory cache in the cloud. The service 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 DBs.
ii. Supports two open-source in-memory caching engines: Memcached and Redis
iii. Elasticache is used to speed up the performance of existing DBs
iv. Way of caching frequently identical queries.

Requirement Memcached Redis
Simple cache to offload DB Yes Yes
Ability to scale horizontally Yes Yes
Multi-threaded performance Yes No
Advanced data types No Yes
Ranking/ sorting data sets No Yes
Pub(Publishing)/ Sub(Subscribing) Capabilities No Yes
Persistence No Yes
Multi AZ No Yes
Backup & restore capabilities No Yes
v. Use Elasticache to increase DB & web application performance.
vi. When the DB is overloaded, what two steps could you take to make the DB perform better – Read Replica and ElastiCache.
vii. Amazon ElastiCache for Memcached is an ideal front-end for data stores like Amazon RDS or Amazon DynamoDB, providing a high-performance middle tier for applications with extremely high request rates and/or low latency requirements.

Question 1:
What are three primary reasons for deploying ElastiCache?
A. data security
B. managed service
C. replication with Redis
D. durability
E. low latency
Answer (B,C,E)

Question 2:
What service does not support session data persistence store to enable web-based stateful applications?
B. Memcached
C. DynamoDB
D. Redis
E. RedShift
Answer (B)

Question 3:
How does Memcached implement horizontal scaling?
A. Auto-Scaling
B. database store
C. partitioning
D. EC2 instances
E. S3 bucket
Answer (C)

Question 4:
What two options are available for tenants to access ElastiCache?
A. VPC peering link
B. EC2 instances
C. EFS mount
D. cross-region VPC
Answer (A,B)

Question 5:
What two statements correctly describe in-transit encryption support on
ElastiCache platform ?
A. not supported for ElastiCache platform
B. supported on Redis replication group
C. encrypts cached data at rest
D. not supported on Memcached cluster
E. IPsec must be enabled first
Answer (B,D)

Question 6:
What caching engines are supported with Amazon ElastiCache? (Select two)
A. HAProxy
B. Route 53
C. RedShift
D. Redis
E. Memcached
F. CloudFront
Answer (D,E)