&gt; <i>Do they expect you to restart when you switch backing services? Do they expect you to run all your internal traffic through load balancers?</i><p>12 Factor was pioneered by Heroku, so yes.<p>Edit: I don&#x27;t understand the downvote. This is the factual answer. 12 Factor apps are supposed to delegate a lot of cross-cutting concerns to the platform, including the problem of &quot;where does that service live?&quot; and &quot;can you give me another chunk of service?&quot;