The default private session state provider in Sitecore Azure

Azure Redis cache is the default private session provider that Sitecore Azure uses. In Sitecore 10.0 and earlier versions, the synchronous session state provider is configured by default:

<add name="redis" type="Sitecore.SessionProvider.Redis.RedisSessionStateProvider, Sitecore.SessionProvider.Redis" ... />

This means that you must configure the asynchronous ASP.NET session module as follows:

<system.webServer><modules><add name="Session" type="Microsoft.AspNet.SessionState.SessionStateModule" /></modules></system.webServer>