Your script has finished all its work, but the process just sits there and never exits. What actually keeps a Node process alive, and how does it decide it's done?

So a Node process stays alive as long as there's still pending work registered with the event loop. That means active timers, open sockets or servers, file operations that are in progress, basically anything the loop is tracking. When the loop has nothing left to do, the process exits on its own. If it's hanging, something is still registered somewhere. The common causes are a setInterval that never got cleared, an open database connection, a server that's still listening, or a stream that was never closed. The usual fix is just cleaning up when you're done. Call clearInterval, close your connections, call server.close(). You can also call unref() on a timer or a socket so it stops keeping the process alive. And if you need to force it, process.exit() ends the process immediately, plus there are the beforeExit and exit events where you can run cleanup code as it shuts down.