Deploying is super slow. Usually it takes a minute or two, which is already quite long, but sometimes something goes wrong and then you can't redeploy immediately. You have to wait a couple of minutes before being able to redeploy.

To be fair, Firebase recently released a local development tool which alleviates the need to deploy on every change, but I haven't used it yet.

https://firebase.google.com/docs/emulator-suite