In this software context, front-end is the collection of templates and static files, including but not limited to css, js, html. The front-end is detached from the back-end. So how visible the catalog icon/link is is entirely up to the front-end being used.

And how it loads is up to the server and client. It's just a basic html with <img> tags. Starting from a more recent version lazy loading is used on those. So if either the server or client is under performing, you will scroll and the lazy loading won't be able to load faster than you scroll.