I've been taking notes for more than twenty years now to have something to turn to when I encounter the same issue I've faced before. On this site I'm collecting most of these into one place mainly for myself but I'll be glad if it helps you as well :)
Command Line Utilities
Command line one liners to solve some problems real quick.
Linux
Linux tweaks, hacks and tricks to make life a bit easier.
Java
Java language, programming and JVM related topics. Memory management, tools, best practices...
Containers, K8s, Cloud
Just as the title says.
Liferay
This section is about Liferay because I spend most of my time with it. I cover mostly infrastructure and performance related topics.