6.6 ElastiCache

Introduction

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 databases.

ElastiCache can be used to significantly improve latency and throughput for many read-heavy application workloads (such as social networking, gaming, media sharing and Q&A portals) or compute-intensive workloads (such as a recommendation engine).

Caching improves application performance by storing critical pieces of data in memory for low latency access. Cached information may include the results of IO-intensive/high-taxing database queries or the results of computationally-intensive calculations.

Two Types of ElastiCache

• Memcached

  • A widely adopted memory object caching system. ElastiCache is protocol compliant with Memcached, so popular tools that you use today with existing Memcached environments will work seamlessly with the service. You don't have Multi-AZ capabilities with Memcached.

• Redis

  • A popular open-source in-memory key-value store that supports data structures such as sorted sets and lists. ElastiCache supports Master/Slave replication and Multi-AZ which can be used to achieve cross AZ redundancy.

Exam Tips

• Typically you will be given a scenario where a particular database is under a lot of stress/load. You may be asked which service you should use to alleviate this.

• ElastiCache is a good choice if your database is particularly read heavy and not prone to frequent changing.

• Redshift is a good answer if the reason your database is feeling stress is because management keep running OLAP transactions on it etc.

• You could also look at using read replicas for RDS.

• You could also look at DynamoDB.

• All in all, pick the best answers from that scenario.