What is the best addition to make WordPress faster?
There are many factors that can affect the speed of a wordpress website, and for each of these factors you can define one more types of solutions. In my case for example, I suffered a lot from the slowness of one of my wordpress sites and tried many alternatives when trying to solve the problem. Since the increase in server capacity, the installation of cache plugins, deactivation and activation of all installed plugins, some people have even suggested using Cloudflare but none of this has resulted in a satisfactory solution.
Until I discovered the real reasons, the real causes of the slowness of my website, the first reason was the innumerable attempts of improper access coming from countries like China and Russia for example and that were taking the use of the server capacity to 100 %, I solved a good part of this problem using analysis tools and blocking by countries on the server. Over time, undue attempts have diminished and today are rare.
The solution to the first problem was half the way, the other half was the outdated server and PHP 5.6. When updating php to 7.0 I noticed that the loading speed of my wordpress site improved a lot, taking from then on a few seconds to display the complete page, but I was convinced that it could improve more, so I analyzed each service and plugin for to know if I could bring the php version up to 7.1 and 7.2, I made this change and the server speed improved again.
Finally, I still noticed a certain slowness on the site, and by executing a simple update command via ssh I could see how important it is to always keep the server up to date, as it is incredible (and obvious) how this routine also helped to improve greatly the speed of my wordpress site and the entire server itself.
Today I have several plugins installed on the mentioned site and I do not depend on cache plugins to keep it loading quickly. But it is logical that for each case there is a different solution (or more than one), so the ideal is always to find out what is the problem that is causing the slowness, and then apply a specific solution.