Restricting file size for an Assets Volume I have a use case where I want to limit the allowed file size for a certain Assets Volume to 20kb. All other volumes should be allowed files no matter the size.

I have looked at some other threads already that suggest developing a plugin to do this, or use the Yii event system for file uploads. 

I have made other simple plugins before that interacted with entries, but I cannot understand how to make a plugin that latches onto the file uploading event.

Does anyone have any good documentation for where to begin with this? It is version 3.0
There's no way for the moment to limit filesize by Volume, but your can create a custom module with the EVENT_BEFORE_SAVE hooked on Assets.

Here's a related post.