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Callback error regularly occurring when app published to GCP

Hi there,

I’m building an ASPNET core app (MVC) that gets published to Google Cloud App Engine (GCP).

Everything works well on my local dev machine, but when published to the cloud about 1/2 the time the request works and the other half it throws error 500 on the /callback URL. (The callback URLs are configure in the “Allowed Callbacks” in the client.)

I suspect this is because App Engine is running 2 server instances (or more under load) and this is playing havoc with the authentication process as the requests will be randomly handled by either of the instances. Does anybody know if any special configuration is required for using Auth0 with App Engine, or can advise if the problem might be something completely different.