Am i the only one who doesn't understand why someone should use a memcache/redis instance hosted by a third party?
I've never used this kind of services but the first impression is that just the RTT between your server and the third party's one will have a huge impact performance-wise, removing every advantage you could have from the use of these DBs.
And what about security? Are memcache/redis/mongoDB/etc... made to be exposed to the public internet (requests content and format are carefully inspected by the server and during development, the implementation have been tested carefully with fuzz testing or similar techniques) or these hosted solutions add an additional layer that increases security/safety?
These issues could be mitigates (not resolved) when both parties are on the same platform, but not everyone is on EC2/Heroku.
