I'd like to implement a 503 feature for my APIs whenever system is in maintenance so that users get the appropriate HTTP response message. As of now, the way I'm doing this is to store a flag in the database and check it with every API request to see if I should be issuing a 503 error. However, I'm thinking there could be a different way to do this on Azure. Is there any setting I could turn on and off on the portal for this purpose so that I don't need to add another lookup trip to the database? I'm using Azure Functions for my services.
You can simply introduce an AppSetting that you check in your function. And then return a HTTP 503. Additionally you can add a timestamp when your API is back and return that in the HTTP header (Retry-After) with your 503.