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by Jiří {x2} Činčura

Azure Functions billing in the absence of function/host key

1 Mar 2020 1 mins Azure, Azure Functions, Cloud

You might be wondering: “Am I going to be charged when somebody invokes my Azure Function but with wrong or missing key?". Well, some of the attendees on my currently running Azure course had the same question. And I thought it might be worth sharing the answer publicly.

The answer is that you’re not going to be charger for executions without or with wrong key. Simple as that. But as I was playing with that, I found something interesting.

Although the function itself is not executed and HTTP 401 is returned, the CPU load increases as the requests are flowing in. Something to theoretically take into account when doing some capacity planning i.e. when not using consumption plan.

Also, if you’re using Application Insights, you get messages in the “log” about the endpoint being matched. Kind of makes sense.

Profile Picture Jiří Činčura is an independent developer focusing on data and business layers, language constructs, parallelism and databases. Specifically Entity Framework, asynchronous and parallel programming, cloud and Azure. He's Microsoft Most Valuable Professional and you can read his articles, guides, tips and tricks at