Prebuilding a cache through a training run will be difficult between lambda invocations though and snapstart[1] already "solves" a lot of the issues a class cache might address.

[1] https://docs.aws.amazon.com/lambda/latest/dg/snapstart.html

Of course, I wouldn't be surprised if the boffins at lambda add some integration between snapstart and class caching once their leadership can get it funded