We have extensive experience in software development, including jobs at industry-leading companies, as well as all the skills required for web performance optimization.
We manage Linux servers (Ubuntu, CentOS, etc), web servers (Apache, nginx), CMS (WordPress, Magento, etc) and do a bunch of other things needed during optimization.
Our work usually includes tests of CPU and IO performance, tuning TCP and TLS protocols to ensure minimal TTFB. Also we can trasfer entire website to another hosting/platform if necessary.
During optimization, we try to keep everything as it was before, avoiding changes. But we are still able to analyze website's code (PHP and JavaScript) and fix it if necessary.
For example, we often tweak WordPress themes to stop loading unused files. Or we can replace CAPTCHA widget with a more performant one. We can also transcode media files, such as images or even videos, for a better ratio of size and quality.
Since our top priority is not to break any function of the website, we always make backup copies of files and database (if any) before starting our work.
In pursuit of higher speed scores, it may be tempting to use asynchronous loading techniques that cause side effects such as FOUC or FOUT. They do not look good, and we always try to avoid them.
Just rely on us!