Merge pull request #668 from jdno/document-aws-regions

Document selection of AWS regions

Author: pietroalbini

src/SUMMARY.md

@@ -51,6 +51,7 @@
     - [Documentation](./infra/docs/README.md)
         - [AWS access for team members](./infra/docs/aws-access.md)
         - [AWS access management](./infra/docs/aws-access-management.md)
+        - [AWS regions](./infra/docs/aws-regions.md)
         - [Bastion server](./infra/docs/bastion.md)
         - [Bors](./infra/docs/bors.md)
         - [CDN](./infra/docs/cdn.md)

src/infra/docs/aws-regions.md

@@ -0,0 +1,56 @@
+# Selection of AWS Regions
+
+The Rust project has deployed a lot of resources on AWS, and most of them are in
+`us-west-1`. As we are growing our footprint and expand to more international
+locations, we are reconsidering which regions we want to use.
+
+Please note that this is mainly for new resources that we are deploying, such as
+new AWS accounts. Existing resources might get migrated, but this is a
+significant effort that might not be worth it given our limited time.
+
+## Selection Criteria
+
+We have two criteria that we use to make this decision:
+
+- **Price** - Pricing differs between regions, and we can reduce our costs by
+  deploying to cheaper regions.
+- **Location** - We want to host our services close to most of our users. But
+  given that Rust is used globally, we won't be able to satisfy everyone.
+
+## Price
+
+Looking at the current distribution of our bill, outbound traffic is by far the
+most expensive item. This severely limits the price savings we might enjoy by
+switching to a cheaper region.
+
+Even if we assume that we will be able to significantly reduce our outbound
+traffic cost on AWS (e.g. by moving to Fastly), the difference between regions
+is not massive.
+
+## Locations
+
+Because most of our traffic comes from the US, we want to run most of our
+infrastructure here. The following regions are interesting to us:
+
+- `us-east-1` or `us-east-2` (cheaper)
+- `us-west-1` (already in use)
+
+Services we want to distribute more globally, e.g. the dev-desktops, we also
+want to deploy to Europe. Here, the following regions seem the most reasonable:
+
+- `eu-west-1` (cheaper)
+- `eu-central-1` (more central location)
+
+## Decision
+
+[We decided](https://rust-lang.zulipchat.com/#narrow/stream/242791-t-infra/topic/meeting.202022-12-12)
+to use the following regions for new resources:
+
+- `us-east-2` - Given that most of our infrastructure is hosted in the US, we
+  want to use a cheaper region here to benefit at least a little bit.
+- `eu-central-1` - Since we're not deploying that many resources to Europe, we
+  want to optimize for location here.
+
+When deploying new resources, they should be deployed to `us-east-2` by default.
+Only resources that need to be geographically distributed should be deployed to
+`eu-central-1`.