Filter design is as necessary to a given website's SEO-driven prospects for high SERP positions as it is to the usability and overall appeal of the website itself from a consumer perspective. It lies at the very core of UX design as a concept and is essentially one of the most important elements for the site's UI design to get right. In this way, it is a direct blend of the separate schools of thought that govern both the user interface and the user experience. Even if a website such as an online storefront arranges all of its wares in distinct categories, without the presence of on-site filters, it would be impossible for the user to avoid having to look through every single product within that category to find something desirable.
Site filters essentially attempt to extract a certain swath of the storefront's overall product catalog and present them as a more closely associated group of results to users who would be much more likely to see any given result within this group as relevant to their interests. While this is extremely useful in allowing a customer to narrow in on a specific desired product, the filter system in place must be designed so that the user can easily and quickly refine an already existing set of filtering criteria. This entails, among many other things, designing its various pop-up menus so that the user is not essentially presented with a small window containing far more items than it can fit, requiring the user to painstakingly adjust its own scroll bar without mistakenly making the window disappear.
Modern filter-inclusive UI design would recommend that the user immediately see any newly selected or deselected option reflected in the dynamically generated product list in the main space of the screen. However, this would naturally cause the site's software to hold up everything until the main list has fully refreshed, potentially interrupting the user's sense of engagement with the site's UI. Advanced scripting procedures would therefore be necessary to allow the UI to continue working even as new results are being loaded. For more information click here https://www.smashingmagazine.com/2021/07/frustrating-design-patterns-broken-frozen-filters/.