This (policy) issue is about to consider the removal of the mongodb cache store from core.

Rationale:

• It was created as a proof of concept when all the muc/caching subsystem was incepted.
• It's unlikely to be used in real prod environments (orders of magnitude slower than other stores like redis, apcu, memcached...)
• The php-mongodb extension is required only because of this cache store and it's a pain to build (~50% of time building PHP images is spent with that extension).
• The mongodb library (that uses the php-mongodb extension) is very hard to maintain, they have refactored it already a couple of times and they are slow providing compatibility with new PHP versions.

Because of all of the above, the proposal is to move this plugin out from core (see MDL-77163). And the two possible outcomes are:

A - Agree, let's move it out.
W - WTF, it's needed, let's keep it.

Ciao