UPDATED
Some might have concerns that sendFile only provides client side caching. There are various ways to have server side caching and keeping inline with the OP's question one can send back just text too with send:
res.send(cache.get(key));
Below was the original answer from 3+ years ago:
For anyone looking for an alternative answer to PavingWays, one can also do:
app.get('/', function(req, res) {
res.sendFile('path/to/index.html');
});
With no need to write:
app.use(express['static'](__dirname + '/public'));
Yes,
app.get('/', function(req, res){
res.render('index.html');
});
should just work