We finally have support for promises in all modern browsers. They give us a nice abstraction to escape callback hell.
A few years ago I worked on an internal management application. One of the mysteries we faced was that it was painfully slow. A page load could take up to 8 seconds. But when we looked at the problem at our local development machines pages loaded within 2 seconds. Not great but a lot better. So I profiled the app looking for something that might cost more in production. After a while about 600 calls to memcached caught my eye.