In Adobe Commerce Cloud, routing configurations for custom domains and subdomains are managed within the .magento/routes.yaml file. This file defines how requests are directed to the application and is essential for setting up different stores or websites with unique subdomains.

Using .magento/routes.yaml for Subdomain Configuration:

To set up a new subdomain, like secondstore.example.com, you need to configure the route in .magento/routes.yaml. This file handles all routing and domain configurations for Adobe Commerce Cloud projects.

Why Option C is Correct:

.magento/routes.yaml is designed specifically for defining routing rules, including subdomains, making it the appropriate choice for this task.

Option A (NGINX configuration) and Option B (.magento/services.yaml) are not correct because they don’t directly manage domain routing in Adobe Commerce Cloud.

Example Configuration:

http://secondstore.example.com/:

type: upstream

upstream: "mymagento:80"