Alexander came to Web development via getting a law degree in his native Germany and teaching English and German as a foreign language in Dnipropetrovsk, Ukraine for a few years. He appreciates that his current field of work is more logical than the law, but sometimes despairs of always facing a screen instead of other people.
AJAX calls have moved user interaction on the Web a huge step forward: We no longer need to reload the page in response to each user input. Using AJAX, we can call specific procedures on the server and update the page based on the returned values, giving our applications fast interactivity.
What AJAX calls do not cover are updates from the server, which are needed for the modern real-time and collaborative web. This need for updates covers use cases ranging from a couple of users collaboratively editing a document to the notification of potentially millions of readers of a news website that a goal has been scored in a World Cup match. Another messaging pattern, in addition to the response request of AJAX, is needed — one that works at any scale. PubSub (as in “publish and subscribe”) is an established messaging pattern that achieves this.