Keys with no timeout

[yaniv-aknin]

I got a report about keys in the cache space having no timeout (expiry) set on them, using Redis as a backend. I believe we always pass a timeout to the underlying werkzeug cache mechanism, so am not sure what to do about this or how to reproduce.

I don't have proper numbers on how often this happens, but I understood it's not entirely uncommon - maybe even more than 1% of keys.

This should be researched further and additional information will be appreciated.