If you looking for a simple tool to draw the Architecture diagram, draw.io is really good and free web tool, click on the link draw.io. The first thing you have to choose is if you want to create a new diagram (see pic 1).

When you have made your choice, the draw.io starts and you can choose a template or build from a blank diagram (see pic 2). You can also name your diagram…

The tool is very easy to learn and you can build a nice diagram rather quickly (see pic 3). On the left side, you can pick shapes and lines. You can also choose to save the diagram local on disk or in the cloud onedrive.

Give the draw.io a try if you need to draw an architecture diagram…