We rely on CloudFlare.com, ElastiCache, and W3 Total Cache to handle WordPress speed. Other factors could have a significant impact on the performance and availability as discussed in this post.
When setting up your WP Je Os server Amazon Web Services presents you with more than a few choices.
Region and availability zone considerations
Amazon explains this here
It seems that an availability zone is an isolated server park within the data center.
Because of this, it might be wise to choose EC2, RDS, and ElastiCache in the same region and availability zone to get the best performance.
Activate your ElastiCache server after activating EC2 and RDS to get the possibility to choose availability zone.
Running servers on different availability zone could make performance suffer. When using the EU-West data center in Ireland make a choice between:
You should make sure that EC2, RDS, and ElastiCache runs in the same availability zone.
The take away:
If EC2 runs on eu-west-1b.
Then RDS and ElastiCache should also be in the server park named: eu-west-1b
Choose the General Purpose SSD (gp2) harddisk wich is the budget friendly alternative. Do not chose the old, slow magnetic storage.
Chose the faster SSD disk and use availability zones for failover.
On EC2 and RDS select Provisioned IOPS SSD (io1) storage. You can choose how fast SSD you want to use. The more IOPS, the better performance, but higher cost. Amazon explains this in detail here.
By choosing all the available availability zones, then you will get failover in case a server park becomes unavailable or slows down. You will also get a higher cost. Failover will only protect you from trouble on the Amazon side. Failover provides no protection against problems related to bad guys, errors, and mistakes related to you, software updates, and the other stuff that sometimes goes wrong. Frequent backup is still required.
ElastiCache is one of the three cornerstones we use to speed up WordPress.