Hello @Jan Rikard Skåret
There are multiple options that you can use to achieve your goals.
- Blue/Green deployment could bring you updates without downtime. To implement blue/green deployment you can use Application Gateway, FrontDoor or Traffic Manager.
https://stackoverflow.com/questions/53418132/blue-green-deployment-using-vsts-release-definitions
- To make your application highly available you can use either Front Door, App Gateway or Traffic Manager.
Consider that App Gateway is regional service comparing to Front Door and Traffic Manager, that are global.
https://video2.skills-academy.com/en-us/azure/architecture/reference-architectures/n-tier/multi-region-sql-server
I would recommend to check Azure Architecture Center and define your requirements(HA, DR, etc) and budget.