Server-side serving “instant” requests means serving more requests (which are usually pretty small) and serving them QUICKLY. Each user will be making loads of smallish requests and need them returned ASAP. The server-side challenge boils down to achieving Low Latency at High Concurrency, which is something of an engineering paradox. Recent advances to tackle what is often referred to as the c10K problem (web servers able to handle ten thousand clients simultaneously) include nginx and node.js.
Redisql is a lightweight SQL server AND Redisql is built on top of the NOSQL datastore redis, supports redis data-structures and redis commands and supports (de)normalisation of these data structures (lists,sets,hash-tables) to/from SQL tables. Redisql can also easily import/export tables to/from Mysql for Data-warehousing.