★ Two modes · one system-design canvas

Design any system.
Or get graded on one.

Sketch an architecture on the whiteboard — then keep it free-form, or let an AI interviewer score it against a real interview brief.

◆ Practice · graded

An AI interviewer scores your design

Real interview problems with a rubric. Hit assess for a score out of 100, what's solid, what's missing, and one concrete next step — pass to unlock the next floor.

✦ Interviewer feedback

REVISE

Strong core: the read path is cached and writes fan out through a queue. But celebrity accounts will hammer a single shard.

✓ Strengths

Cache-aside in front of the feed DB
Fan-out workers decouple writes via a queue

△ Gaps

No plan for celebrity fan-out (the hot-key problem)

→ Next

Add a per-user feed cache and go hybrid: push for most users, pull for mega-accounts.

▶ Climb the tower

◇ Design · free

Or sketch anything on a blank board

The full component kit, no brief, no grading. Drag, wire, annotate, import a Mermaid diagram, and share a link so others can remix it.

Drag · wire from the ◦ port · click a line to cut

✎ Open a whiteboard

Free to play, no login required. Log in to save your climb and your whiteboards across devices.

NEW Download the MCP server · for AI agents

Let your AI agent draw the design

Add the Blueprint MCP server and your AI assistant — Claude Desktop, Claude Code, Cursor — sketches system designs straight onto an editable Blueprint whiteboard, then hands you the link. Three steps, no local install.

1 Generate a key

Create your MCP key →

2 Install (Claude Code)

Drop your key into one command — npx fetches the server, nothing to install.

claude mcp add blueprint \
  --env BLUEPRINT_API_KEY=bp_your_key \
  -- npx -y systemsdesign-mcp

Claude Desktop / Cursor (JSON)

{
  "mcpServers": {
    "blueprint": {
      "command": "npx",
      "args": ["-y", "systemsdesign-mcp"],
      "env": { "BLUEPRINT_API_KEY": "bp_your_key" }
    }
  }
}

3 Use it with Claude

Just ask:

"Design a URL shortener and share it as a Blueprint link."

→ Claude draws it and returns an editable /s/… whiteboard link.

⬇ systemsdesign-mcp on npm ↗ Docs & source ↗

Logged-in only — your key ties every diagram to your account. Works with any MCP client.

Vendor-neutral by design

The palette is built from generic primitives (cache, queue, gateway, object store, stream processor), not DynamoDB, SQS or Pub/Sub. You reason about the roles in your architecture instead of memorizing one cloud's product names, so the design instincts you build here transfer to any interview, any stack, and any provider. That's exactly how a strong interviewer wants you to think.