Nodejs in-memory storage

node-cache package is currently the best for key value store and it allows synchronous as well as async storage/retrieval/deletion of keys.

npm link

The server that node.js allows you to build, is an application server, which means that state is preserved, between request, on the server side. The following snippet demonstrates this:

var sys  = require('sys'),
    http = require('http');

var number = 0;

http.createServer(function (req, res) {
        console.log(req.method, req.url);

        res.writeHead(200, {'Content-Type': 'text/html'});
        res.write('<h1>Number is: ' + number + '</h1>');
        res.end();

        number++;

}).listen(8000);

sys.puts('Server running at http://127.0.0.1:8000/');