Dynamically Create Subdomains for SaaS Application


SaaS platform generally has multiple tenants. General practice is to provide a dedicated subdomain for each tenant. For eg. <tenant-name>.<domain>.com. This article describes how it can be achieved via AWS Route 53 wildcard DNS entry.


Implementing Dynamic subdomain has several challenges


  • How the new subdomain will be configured and published in DNS?
  • How does the SSL certificate gets signed for every new subdomain?
  • How the new subdomain is configured and published on Webserver?
  • How does the SaaS web-tier know about the new subdomain?


Enter the wildcard DNS record. A wildcard DNS record matches any subdomain of that domain name.


*.onlinetutz.com ->


This means any subdomain for onlinetutz.com will now resolve to For eg:



Creating Wildcard DNS in AWS Route 53


  • Create a Public/Private Hosted Zone.
  • Create a recordset with * in the above-hosted zone and map it to the server or ELB.


Creating Wildcard DNS in AWS Route 53


Creating Wildcard DNS in AWS Route 53


Testing the Setup


For testing the setup, below python script which is based on Flask framework can be used.


from flask import Flask

app = Flask(__name__)
app.config['SERVER_NAME'] = 'onlinetutz.com'

@app.route('/', subdomain="<tenant>")
def index(tenant):
    return "Tenant Name:" + tenant

if __name__ == '__main__':




From the below output we can confirm that we are able to route to subdomain on-the-fly and also fetch the information regarding the subdomain.


[ubuntu@ip-12-11-52-34 ~]$ curl http://facebook.onlinetutz.com
Tenant Name:facebook
[ubuntu@ip-12-11-52-34 ~]$ curl http://google.onlinetutz.com
Tenant Name:google
[ubuntu@ip-12-11-52-34 ~]$ curl http://twitter.onlinetutz.com
Tenant Name:twitter