It runs, then it does not. Nine times out of ten it is one of four things, and none of them require understanding the code that broke.
Your app works until you close the laptop. Here is what actually keeps it online, what each option costs, and why the free tiers stop working after a few weeks.
An honest description of who gets value out of this, including the cases where you should use something else.
These tools get you to a working app fast and then the hosting question arrives. What each one gives you, where it stops, and what to do when your project outgrows it.
You built the app in an AI editor. You can deploy it from the same window over MCP, without a CLI, a Dockerfile or an API key.
Both are mature, both are maintained, and the answer is mostly about which language you already write. Here is the honest comparison, including where they genuinely differ.
Functions and containers solve different problems. Picking the wrong one produces either surprising bills or an app that is asleep when it matters.
Where the token goes, why .env does not get deployed, and how to stop a leaked secret from being a rewrite.