The webapp is currently configured to run on two instances.
Since you have only two instances you can expect a downtime of upto 50% because when the App Service platform is upgraded, the instance on which your web app is hosted will be upgraded. Therefore, your web app process will be restarted and may experience some downtime as each instance is restarted sequentially.
Solution
Scale out to three instances. These instances are in different upgrade domains and hence will not be upgraded at the same time. While one worker instance is getting upgraded the other is still active to serve web requests.
Scenario
The webapp is currently configured to run on two instances.
Since you have only two instances you can expect a downtime of upto 50% because when the App Service platform is upgraded, the instance on which your web app is hosted will be upgraded. Therefore, your web app process will be restarted and may experience some downtime as each instance is restarted sequentially.
Solution
Scale out to three instances. These instances are in different upgrade domains and hence will not be upgraded at the same time. While one worker instance is getting upgraded the other is still active to serve web requests.
simple-report-api-prod/troubleshoot Scale instance count manually or automatically