Please hold: your call is in a queue. An introduction to queuing in Drupal.
My talk from Drupalcamp London 1st-3rd March 2013. A version of this talk with minor modifications was also given at the Drupal Learning April 2013 meetup in London (http://www.meetup.com/Learning-Drupal-Meetup/events/111107222/).
It's not just the Brits that love queues, Drupal loves them too.
Maybe your website is making requests to another internal or third party system. Maybe a third party is sending messages to you. Either way, as you begin to grow your services are increasingly likely to run into problems completing these requests in a predictable amount of time and with guaranteed success.
Queueing is one solution to this, balancing load, ensuring jobs are processed successfully - but the uses don't end there.
This session will provide an overview of queueing patterns, discuss some scenarios where you may want to implement queues, and look at how Drupal implements queueing - as well as some of the gotchas in implementing queue processing at scale.