Likely Arcentry. Another company in the space is https://cloudcraft.co/

What's kinda mind blowing is that this is an actual business. I can't imagine why someone would need this specifically for their cloud presentations. Like isn't visio enough for everything?

Wow! So the original story is written on the blog of a company that is creating Chart of clouds architectures (and probably being on the edge)? I'm amazed by how niche that business is!

also very nice plug to put your diagrams into the story

Right, I didn't even make the connection until the OP asked the question here.

It has been fifteen years since I had access to a machine with Visio installed, and my memories from back then aren't good memories. This seems more like a descendant of GraphViz than anything to do with Visio.

I personally don't use it, but I know nearly everyone in my company does. (F500, >300K employees)

What does "open-source" refer to in "Create beautiful cloud and open-source diagrams"?

As in it offers components that are unrelated to any cloud provider. Postgres, Nginx, Kafka etc.