If you were a small business, and wished to remain small, I would not tell you to use a custom CMS. In fact, I would be wary of recommending any proprietary systems, let alone a system designed specifically for one site. The reason behind that is because to pay for a custom CMS, you’d be getting way more than you might be using. Plus, you’d be paying to re-invent the wheel for all the functionality of a brochure-ware site. I would, instead, suggest putting that budget towards differentiating yourself on design and search engine marketing. The vast majority of the sites on the Internet today would fall into this group. They don’t need any more functionality than a simple blog or page management system like Wordpress or Drupal offers.

The lines start to become blurred when we start talking about high performance websites. The lines become even more blurred when we talk about custom user-facing functionality and integration into back-office systems.

To use our example from above, Wordpress and Drupal are great Content Management Systems. You can get decent performance out of them with a bit of effort in configuration and deployment, maintenance, purchasing extra hardware/setting up reserved instances to handle traffic spikes and generally beating it into submission. At its heart though, it’s just something to manage a traditional model of a website: a collection of pages. Would you use Wordpress (or something like it) to manage something like Facebook? No! Of course not! That is because Facebook has custom functionality and features that are not part of a standard website.

Building high performance websites, whether eCommerce or informational, requires more work than your typical website: they are custom applications with a very rigid set of requirements for performance, responsiveness and search engine optimization capabilities. The amount of time spent on bending another CMS into working how you want it and to function at the level of performance required would give you a sub-par product and often takes longer than building it from scratch.