Addressing GT Metrix Reports
GT Metrix is a popular tool for testing page speed issues and loading times for websites, however, its results are not always as accurate or easily understood as one may hope.
We have received reports of Spotlight being diagnosed as a potential cause for an increase in page load time when tested with GT Metrix. Here's a look at how Spotlight actually works and why the GT Metrix reports aren't a true representation of how things work in the real world.
When going through a GT Metrix report's Waterfall, you may see Spotlight's POST requests. These types of requests are typically done asynchronously. That means they happen in the background without slowing down the page's initial rendering. They typically request data from the server, not content such as images, fonts, styles, etc. In Spotlight's case, the POST feed request asks the server for the feed's posts.
The reason why we say that this does not affect the initial rendering is that Spotlight is "done" the moment its JS loads on the page. From then on, it will show the grey flashing boxes to indicate that it's loading the posts. When the POST feed request comes back with a response, the grey boxes are replaced with the actual posts, which will then load their thumbnails as the browser downloads the images.
During this time, the browser is still loading everything else - all because browsers are very good at loading multiple things at the same time. You may see in the waterfall that during the request's time, the GT Metrix browser would also be downloading a lot of other resources (in most cases, other images on the page). Contrast that with other possible requests on your website, such as jQuery and Autoptimize. These typically block everything else until they're done (partially or completely), with nothing else able to be loaded in the meantime.
Therefore, Spotlight's contribution to any suspected delay in page-loading is not a problem for a WordPress site. In fact, we continue to improve Spotlight's performance even further over time.
You may find other plugins that don't show such results in GT Metrix, however, with the ones we've tested, that's only because their feeds are part of the initial page load, causing the delay there and not showing up as their own listing in the Waterfall report. With Spotlight, we chose to make it asynchronous to have even less of an impact on the overall page loading time.
If you'd like to use that method, we have added a preload option in Spotlight's Configuration settings which removes the asynchronous POST feed request in exchange for slightly increasing the page load speed.