Why do programmers databases with JavaScript? Lua is more embedded language than JavaScript. http://www.aerospike.com/ http://redis.io http://tarantool.org use LUA and it more powerful and easy to use as procedures.
I am surprised that nobody mentions the great performance of Google's V8 engine here...
And the constant performance improvements over the last years, that are the result of the ongoing race for better performance between the browser vendors.