Asynchronous processing

Slow operations should be done asynchronously to avoid making users wait for long periods of time until their requests are processed.

Sometimes this can be done in advance, by pre-processing data that you know users will need. For example, a forum might periodically re-render its page of most popular posts and the number of comments.

Asynchronous processing usually requires 2 components:

1. A queue that stores tasks, ordered by time and priority
2. A system that processes tasks