I am deploying my custom Keycloak Docker image (based on version 15.0.1) to Azure App Service. My App Service plan was initially B2 and I got timeouts. After around 240 seconds, Azure stopped the App Service because it was not responding. When I enabled DEBUG logging, I could see that is was busy creating the database tables in the PostgreSQL database (also hosted on Azure).
The only way to fix it was selecting the B3 plan. Note that I manually had to clear out the database, otherwise, Keycloak tried to create tables that it already had created. Maybe it got interrupted halfway and it did not record how far it got in the
Anyway, not much that can be done about it I guess. But I wanted to put this out there in case somebody else looses a day trying to figure out why it is not starting properly.