I think the key architectural mistep is putting a colab session per user session. A fix is having the user call out to an service API, which, behind the scenes,

I think the key architectural mistep is putting a colab session per user session. A fix is having the user call out to an service API, which, behind the scenes, is executed on a pool of colabs with reuse. I don't know of any technology to make that easy though. The symptom that could of been a trigger for cost investigations were the long startup times.