Supaboard - Practice system design interviews with AI mentorship

Hey PH! I'm Andre, eng lead based in Vancouver. I've interviewed a lot of engineers for system design rounds over the years. The pattern that kept bugging me: candidates clearly understood the theory but fell apart when they had to actually build something from scratch. They'd watched all the YouTube videos, memorized the classic walkthroughs, but give them a slightly different problem and they'd freeze. Same thing when friends asked me to help them prep. We'd jump on a call, I'd give them a prompt, and they'd just freeze from time to time, not knowing what to do next. The problem was never that they didn't know what a load balancer does. It's that they'd never practiced going from a blank page to a full architecture while tracking requirements and defending their choices out loud. And when I wasn't around to run the mock? They had no way to get feedback. That was the real gap. You can practice drawing diagrams all day, but without someone pushing back on your decisions and asking "what happens when this fails?" you're just reinforcing your own blind spots. So I built Supaboard. It's a whiteboard with system design components, a requirements tracker on the side that works like how interviewers actually score you, and a gallery where people share their designs. The two newest additions are what I'm most excited about. Challenges give you a real prompt with requirements, like I'd give someone in a mock. And the AI Mentor looks at your actual diagram and asks hard questions about tradeoffs and failure scenarios. It's basically the feedback part of the mock interview, available anytime. Free to use. Would genuinely love to know what system design topics you'd want to practice, I'm actively building more challenges.