Multitenant domain routing with AWS Route 53

A common requirement in SaaS applications is the ability to route requests to different tenants based on a URL routing strategy.

In most cases, a domain prefix is good enough to identify tenants (e.g. mytenant.xxxxx.com). That approach typically relies on CName records for mapping the prefixes or tenants and the domain name to an URL where the application is actually hosted. Many cloud providers support the idea of mapping custom domains to their web hosted services, so this approach with CName works just fine.

An evident problem is that you would require a different CName record per prefix or tenant. If you have to create those records manually, this approach simply does not scale as the number of tenants increase.

An alternative is to use a wildcard CName, and route all the requests that match that wildcard to the hosted application in the cloud. For example, *.xxxxxx.com to your web application url.

Many DNS servers don’t support wildcards in CName such as the ones offered by free for GoDaddy or NameCheap. However, AWS Route 53 supports wildcards and also an API to manage almost everything in the DNS tables.

Configuring AWS Route 53 is relatively easy. Assuming that you already have a AWS account, you need to create first a hosted zone, which represents the association of a domain name with a set of name servers provided by Route 53. Once you specified the domain name (e.g cibrax.me), and the hosted zone is created. Route53 will show you a list of name servers you need to use. If you already own a domain in other place like GoDaddy or NameCheap, you need to go there and update the list of name servers associated to that domain.

Afterwards, you need to create a resource record set, which is basically the CName record containing the wildcard or prefix you want to use. Here, you can specify the CNAme record and the mapped URL. For example, *.cibrax.me goes to www.xxxxxxxx.com.

That’s all from the point of view of DNS configuration. The rest is part of the implementation of your web application.