Skip to content

System Design Simulator

Visual drag-and-drop system architecture builder with components, connections, templates, and export — perfect for interview prep

System Design Simulator

100%
🏗️

Drag components from the palette or load a template

Click ports to draw connections between components

0 components · 0 connectionsAlt+drag to pan · Ctrl+scroll to zoom · Del to delete

Last updated:

This tool is provided as-is for convenience. Output should be verified before use in any production or critical context.

For AI agents: how to call this tool

Machine-readable contract, endpoints and examples. Humans can ignore this section.

Best Path For Builders

Browser workflow

Runs instantly in the browser with private local processing and copy/export-ready output.

Browser Workflow

This tool is optimized for instant in-browser execution with local data handling. Run it here and copy/export the output directly.

/system-design-simulator/

For automation planning, fetch the canonical contract at /api/tool/system-design-simulator.json.

How to Use System Design Simulator

  1. 1

    Drag-and-drop architecture components onto canvas

    Start with blank canvas. Drag servers, databases, caches, load balancers, message queues onto the board. Position them logically (front → app → cache → db). Visual system design.

  2. 2

    Connect components with arrows to show data flow

    Draw arrows: Client → Load Balancer → App Server → Cache → Database. Label arrows with protocols (HTTP, gRPC, SQL). Visualize request flow through your system.

  3. 3

    Add annotations for capacity, latency, and throughput

    Label server nodes with specs (4CPU, 16GB RAM), database with throughput (10k req/s), cache hit rate (95%). Add latency estimates. See where bottlenecks are: slow DB? Low cache hit?

  4. 4

    Test scaling: what happens if load doubles?

    Original design: 2 app servers, 1 database. If traffic doubles, bottleneck shifts: app servers fine, but DB maxes out. Drag in another DB replica or add read replicas. Simulate scaling strategy.

  5. 5

    Export and document system design for team

    After designing, export canvas as image or PDF. Share with team. Much clearer than 'we have a load balancer and three app servers.' Visual documentation for onboarding and discussions.

Frequently Asked Questions

What is the System Design Simulator?
A free visual tool to build system architecture diagrams by dragging and connecting components like databases, load balancers, caches, message queues, and microservices onto an interactive canvas.
How do I use the System Design Simulator?
Drag components from the left palette onto the canvas, then click the ports (small circles) on components to draw connections between them. Use the Templates dropdown to start from common architectures like URL Shortener or Chat App. Edit labels and properties in the right panel.
Is the System Design Simulator free and does it store my data?
Yes. Free to use with immediate access—no account required. Everything runs 100% client-side in your browser — your architecture diagrams never leave your device. Export as JSON to save and re-import later.
Can I use this to practice for system design interviews?
Absolutely. Load a template like URL Shortener or Chat Application, modify it, or build from scratch. The component library covers all major distributed system building blocks you'll encounter in FAANG-style interviews including load balancers, caches, message queues, and databases.
What export formats are supported?
Export your diagrams as PNG images for presentations, SVG vectors for high-quality scaling, or JSON data to save and re-import your architecture later. All exports are generated client-side with no server involved.