Your app is live. Here is what breaks first.

Database connections

The first thing to go, and the most confusing, because it is intermittent. Some people load the page fine; others get an error; you refresh and it works.

The cause is usually that each request opens its own database connection and the database has a limit. One user never approaches it. Twenty at once do. The fix is connection pooling, which is configuration rather than code.

Errors nobody is recording

Something fails for a user, they see a blank screen, they leave, and you never find out. This is worse than a visible outage because it is silent and it lasts.

Two things fix it: showing the user something useful when a request fails, and recording errors somewhere you will actually look. Neither is a large job, and AI tools generate the happy path almost exclusively, so assume neither exists.

Credentials that expire

API keys get rotated, OAuth credentials expire, free tiers hit their ceiling, and certificates lapse. Each one fails at a moment unrelated to anything you did, which makes it feel random.

Write down every external service your app depends on, what credential it uses, and when that credential expires. It is a fifteen-minute document that saves an afternoon of confusion later.

Storage with no rules

File storage has its own access rules, separate from your database, and they are missed almost every time. If users upload anything — documents, images, anything private — check whether the storage rules match the intent of your database rules.

A file URL that works when pasted into a private browsing window is a public file, whatever the app implies.

The one thing to set up before you need it

A database backup you have restored at least once. Every provider offers backups; far fewer people have ever tested restoring one. A backup you have never restored is an assumption, and the moment you find out is the worst possible moment.

What does not usually break

Worth saying, because launch anxiety tends to point at the wrong things. The interface generally holds up fine. The framework is not going to fail you. The hosting is not going to fall over at the traffic a new product gets.

What breaks is the seams: the places where your app talks to something else, under conditions you did not test because you were the only person using it.