Who do you call when your website needs fixing?

For many small businesses, launching a website is only the beginning.

A plugin breaks.
A page stops working.
The website becomes slow.
A new feature is needed.
Something needs to be updated.

But who handles it after launch?

I'm a Website Developer, and I work with businesses and individuals on website development, updates, bug fixes, performance, redesigns, new features, and ongoing maintenance.

I'm curious how others handle this:

Do you have a regular developer, maintain everything yourself, or find someone whenever a problem comes up?