Redis is the best data store I've had the fortune to work with. No nonsense data structures coupled with extremely reliable performance, beautiful API and extremely easy to manage.
It also helped me earn a lot of praise for using redis-cli --pipe to bulk insert data which bringed down a data import job to a few minutes from 4 hours. I eventually built a wrapper around redis-cli --pipe for using it with a cluster.
Try inserting more that 30K elements in a key which is a sorted set and watch the insertion time, memory & cpu usage. Now try doing this to millions of keys simultaneously.
It also helped me earn a lot of praise for using redis-cli --pipe to bulk insert data which bringed down a data import job to a few minutes from 4 hours. I eventually built a wrapper around redis-cli --pipe for using it with a cluster.