In case of WordPress it’s quite easy to hire an over-experienced developer, making them bored at work, and unnecessarily increasing HR costs for project managers.
So it’s important to hire based on the scope of the website that has to be built – a simple landing page won’t require extensive web development experience, but a multi-site system will be much harder to build, and thus require larger experience.
A great WordPress developer knows just how to tweak and fine-tune the system to meet any website’s needs, without compromising security with unnecessary and untrustworthy plugins, and without messing up the back-end.
The necessary skillset of a WordPress developer depends on the requirements of the website that needs to be built. It depends on what functionalities are expected, on how many people will be using the website, on how much control over the content is required, and what type of data the site is going to use.
In some cases, managers might want to hire a front-end developer only to create a custom theme for their WordPress website, however a good way to save costs is to use one the endless readymade WordPress themes (a lot of them are free to use).
WordPress developers should have a deep understanding of CSS (selectors, properties), HTML and best practices for manipulating HTML elements, and experience working with different web development frameworks, libraries and preprocessors like LESS and Bootstrap.
At its core, WordPress uses several JS libraries, so knowing libraries like Angular can come in handy for the developer.
Knowledge of PHP, the fundamental language in WordPress, is another important skill. WordPress uses a relational database management system, so knowing SQL and MySQL is key to understanding the WordPress database structure.