For anyone coming across this hoping to store your access tokens this way (m2m token caching being the given example) check this thread out: Caching M2M access token in Actions - #3 by rueben.tiow
TLDR:
Cache keys have a maximum size of 64 bytes and values have a maximum size of 2048 bytes
Which means that they can’t be used for caching tokens unless you split the token up. Was this use-case tested before the feature was rolled out and marketed?