I wanted a system-design lab that could prove me wrong

When I practice system design, the part that has always felt a little unsatisfying is that the diagram usually gets the final say. You can draw a load balancer, put PostgreSQL behind your application servers, add a private subnet, and end up with something that looks perfectly reasonable. But the diagram itself never proves that PostgreSQL is actually private. That is the idea I kept coming back to while building Torollo : What if the diagram was only the intended architecture, and the running system was the thing that decided whether you were right? That became the core of the project. The architecture actually runs Torollo is a local system-design lab. You build an architecture visually, but the nodes on the canvas are backed by real Docker resources on your machine. If you add a server, there is a container behind it. If an exercise uses PostgreSQL, PostgreSQL is actually running. If the architecture introduces network boundaries, Torollo has real Docker networking underneath them. The roadmap then validates the environment that exists instead of checking whether your diagram looks correct. One of the free roadmaps, for example, has you build a resilient three-tier application. You start with a web server and a database, then progressively introduce: a load balancer multiple web servers network restrictions failure scenarios At one point, PostgreSQL is supposed to be isolated from the load balancer. Torollo actually checks that. If the load balancer can still reach PostgreSQL on port 5432 , the step fails. You change the configuration, run the validator again, and the step only turns green when that connection is really blocked. That loop ended up becoming the part of Torollo I care about the most: Build something → make an assumption → let the runtime prove whether the assumption is true. The canvas is only one layer The frontend is built with: React TypeScript React Flow The backend uses: Node.js Express TypeScript Dockerode But I try to keep a strict separatio