Regions and Availability Zones

AWS has really mature and global infrastructure divided into Regions and Availability Zones. Region is AWS infrastructure located in one geographic location. AWS Regions provide close to each other datacenters/locations called Availability Zones (AZ) which are connected with fast, private fiber-optic networking. AZ are physically isolated so failure of one AZ shouldn’t impact other AZs in the same Region. Each Region has two or more AZ, except local region – Osaka – enabled only on customer requests. Currently AWS has 18 Regions, 55 AZs and announced 4 more Regions that are one the way, including one in Europe – in Sweden.

Edge Network Locations

An edge location is where end users access services located at AWS. Keep in mind that they are something different than AZs. They are situated in most of the major cities around the world and are specifically used by CloudFront (CDN) to distribute content to end user to reduce latency. It is kind of front end/cache content for the service which are located in AWS datacenters. In Poland there is one Edge Location in Warsaw.

Design Considerations

• Always make use of Regions and AZs when designing your infrastructure and application to make them highly available – I will describe some common use cases in further posts.
• Replication between Regions is not automatic so if you need multi region high availability you need to do it yourself.
• Availability Zones identifiers are created for each account randomly. For example, your Availability Zone us-east-1a might not be the same location as us-east-1a for another account.
• Not every Region has all new services, typically new service is enabled first in USA and later in EU (starting from Ireland).
• There is special Region GovCloud that is available only to government customers.

Costs

When designing application using multiple AZs or Regions you need to take into consideration costs:

• Data transfer between AWS services located in the same region but in different availability zones is considered as regional data transfer and is charged at $ 0.01/GB (outgoing data transfer).
• Data transfer between AWS services and across AWS regions is treated as internet data transfer and is charged at $0.02/GB (outgoing data transfer). These costs fluctuate a lot depending on the region e.g. all data transfer from AWS Singapore to other AWS regions is charged at $0.09/GB.
• Data transfer into an AWS region from any service in any other region is free.
• Data transfer costs for transferring data in the same region and within the same availability zone are zero, with one caveat. You must be using a private IP address.

Reference Materials:

AWS Global Infrastructure
AWS Podcast: Making the Best Use of AWS Regions, Availability Zones and More