I’m working on an app that automatically assigns subdomains to projects that people create through it (like Slack does with my-slack-org-name.slack.com subdomains for Slack orgs). People can also assign custom domains to projects they create on the app. I’m trying to evaluate which Elixir hosting service to use it on based (in part) on how easy/difficult it is to handle setting up custom domains and subdomains.
Heroku has a limit of 1000 custom domains per app, which makes it a non-starter for my project.
Gigalixir doesn’t limit the number of associated domains, except for adhering to Let’s Encrypt’s rate limits, and does let you assign them via an API, but for wildcards you have to provide certs yourself and contact them to get them setup — wildcard certs can’t be created via the API.
It looks like fly.io’s API lets you add custom domains including wildcards via the API. Is that correct? And are there limits to the number of domains that can be associated with a specific app?