Hierarchical-MVC has been shown to make large web applications easier to scale out, but there is a price to pay- namely overall performance. This article will investigate ways of improving performance within HMVC web applications using asynchronous processing and some good old caching techniques. Predominantly this article will use examples written for the Kohana Framework; however all the concepts portrayed here could apply to any framework or web application.

He starts by pointing out what's wrong with the typical HMVC application - namely that the clean separation of code structure (the hierarchical part) costs the application in overall speed and memory usage. He suggests a simple technology for helping ease the load - caching as much information as possible, mostly in the HTTP client code since HMVC applications rely heavily on it. Code samples includd show how to implement this in a simple Kohana application.

It can also be very costly in time and resources to re-architect software that not scaled well. Ideally applications should grow organically as required and without large sums of money being exchanged in the process. [...] The Hierarchical-Model-View-Controller (HMVC) pattern is a direct extension to the MVC pattern that manages to solve many of the scalability issues already mentioned [in this post].

He talks about the benefits of the HMVC style and how its multiple parts work together and how it promotes code reuse more than the traditional MVC pattern. Some sample code is included so you can get your hands dirty with more than just the concepts behind the pattern including a more real-world example, their service (Gazouillement) that works similarly to twitter.

I recently had fun with an all-to-common issue with SQL driven websites: hierarchical data. For those who don't like big words, think trees. Other people have already discussed storage methods, and I would actually highly suggest you read the writeup if you haven't already.

He includes a sample table you can work from and some code that can be used to generate a select (based on a $depth variable) parent/child values from it. A few simple function calls later and you have a nested array or lots of little subarrays maintaining the parent/child relationships the database has.