The ask is to flatten a multidimensional space into a 2D plane, so out of the gate you're going to have problems. A really good architectural diagram doesn't have a lot of crossed lines, but you can only really do that when you have a small number of nodes or when the dataflow is broadly unidirectional.
The interview is inherently unfair - when you use a drawing tool to build diagrams the work is iterative, but erasing marker during an interview looks like you've made a mistake.
Start with a small top-level diagram, then build a hierarchy of increasingly detailed diagrams. Use the opportunity to steer the interviewer ("which area would you like to see in more detail?"). It also helps to have an understanding of how small bits of code map to graphical sketches, so that you can compose them later.
Also, keep in mind that issues like poor handwriting and sloppy lines are exacerbated by large detailed diagrams.
The interview is inherently unfair - when you use a drawing tool to build diagrams the work is iterative, but erasing marker during an interview looks like you've made a mistake.
Start with a small top-level diagram, then build a hierarchy of increasingly detailed diagrams. Use the opportunity to steer the interviewer ("which area would you like to see in more detail?"). It also helps to have an understanding of how small bits of code map to graphical sketches, so that you can compose them later.
Also, keep in mind that issues like poor handwriting and sloppy lines are exacerbated by large detailed diagrams.