var DB = require('db');
var cache = require('proxy-cache');

var db = new DB();
db.getUserById('id', function (err, user) {
  // fetches `user` from the db
});

db = cache(new DB(), ['getUserById']);
db.getUserById('id', function (err, user) {
  // fetches the user from the db 
  // and caches it in memory as `getUserById:id`
  db.getUserById('id', function (err, user) {
    // this lookup fetches `user` directly the from the cache
  });
});

{
  max: 10000,
  maxAge: ms('1m'),
  stale: false,
  peek: true, // peek by default so maxAge is honored
  tombstone: true // save undefined values returned as well
}