Long story short:
Is there a practical recommendation for hardware and PHP configuration for Matomo? If you have 1 billion visitors per year with about 3 actions per visit. And data / logs are deleted after 365 days.
We regularly use instances like Cloud Hosting - High Performance And Reliability! -> “Configure your own cloud”
1 billion visitors per year with about 3 actions per visit -> ~ 100 actions per second
Tests with Matomo have shown that the available CPUs are used only to a limited extent. Like 32 available CPUs, but a maximum of 8 CPUs were used under Matomo / PHP 7.2.