Allow component cache to use alternative backend

[divmain]

Everything is in-memory for now. However, caching is done with simple keys. And once a cached component has been compressed, the values stored are simple strings. This being the case, there's no reason why Redis couldn't be used as a backend.

Several benefits come to mind:

• TTLs for cache entries become simple to manage
• you don't risk out-of-memory errors in your Node process for folks caching anything and everything
• this scales across nodes
• you could also prime your cache using known keys

[ryan-roemer]

Or really, any distributed cache service (memcached, ElasticCache, etc.). Should be a pretty simple abstraction layer.

Put another way, I wouldn't tie it to Redis 😉

[divmain]

Agreed. I've expanded my thoughts in the description for why Redis provides such great synergy. But you're right - any caching service should be usable. Ideally, the abstraction is agnostic to the storage, i.e. you're only responsible for providing get and set functions that return a Promise.

[divmain]

Related to #5. It may be that this issue is invalidated, if we recommend a "real" caching backend for "real" deployments.