Honest Consultancy. Updated
What is eu-west-1?
It is the code name of the AWS Europe (Ireland) region. Every AWS region is made up of separate Availability Zones, and AWS lists three for eu-west-1.
Spread production workloads across at least two Availability Zones so the loss of one does not take the service down.
Zone names such as eu-west-1a map to different physical zones in different AWS accounts. Use the Availability Zone ID (for example euw1-az1) when you need to line up zones across accounts.
Is every AWS service available in eu-west-1?
Most are, but not always on the same day or with every instance type. Check the AWS regional services list before you commit to a design.
New instance families and new services often reach US regions first. If a design depends on one, confirm it is offered in eu-west-1 before the work is agreed.
What does data transfer cost?
Data coming into AWS from the internet is free. Data going out to the internet is charged per GB after a free allowance of 100 GB a month, pooled across all regions.
Traffic between Availability Zones and between regions is also charged. Chatty services spread across zones, or replicas in a second region, can add up quietly.
Check the current per-GB rates on the AWS pricing pages rather than relying on older figures.
Should we also use a second region?
Only if your recovery targets need it. A second region roughly doubles what you run and adds inter-region transfer, so decide from the recovery time you actually need.
