Look into jussi:

https://github.com/steemit/jussi

It's a json-rpc reverse proxy specifically designed to sit in front of steemd and use a redis cache.

It will also route other json-rpc calls that start with other prefixes (e.g. sbds.) to other backend services other than steemd, which comes in handy when you want to run sbds (https://github.com/steemit/sbds) alongside on the same endpoint... like https://api.steemit.com.

Steem on!