Litany of failure here: https://twitter.com/theshawwn/status/1174480402779648000
Perhaps I just got unlucky and the situation is improved now. But it was a waste of a day for me.
Sorry about that. We (I) had screwed up and allowed users to smash themselves into the wall of "Huh, you keep getting preempted, but there's technically a slot right here". We've re-enabled some backpressure to keep you from getting hit over and over again, and instead see a stockout error when you should probably try another (less full) zone.
I doubt it makes a material difference to their (or our) bottom line, but it's just a nice gesture and makes you never feel like "damn, I literally wasted money".
To me, they're not really sold as "cheaper, just not 100% guaranteed"; they're sold as "cheap, it will be killed at any moments notice so".
I should test more at some point.
Reading between the lines of both the signup page and up-to-date FAQ, it seems like the free TPU in Colab notebooks will be depreciated, which isn't too surprising.