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System Design Simulator

Drag databases, caches, queues and load balancers onto a canvas, connect them, start from six templates, and export the design as PNG, SVG or JSON.

System Design Simulator

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HTTPSRound robinRound robinSQLGET/SETSQLGET/SET
💻Browser
⚖️Load balancer
⚙️API Server 1
⚙️API Server 2
🗄️PostgreSQL
⚡Redis
6 components · 7 connectionsAlt+drag to pan · Ctrl+scroll to zoom · Del to delete

Updated . Provided as is. Check the output before you rely on it in production.

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

    Select a component to set its label, tech stack, description and QPS or throughput in the Properties panel.

  4. 4

    Test scaling: what happens if load doubles?

    Duplicate app servers, add caches or read replicas, and reconnect the flow to compare designs. The tool is a diagramming aid; it does not compute load.

  5. 5

    Export and document system design for team

    Export the canvas as PNG or SVG for documents and slides, or as JSON to re-import and keep editing later.

Questions and answers

What is the System Design Simulator?
A system design diagram shows how services, databases, caches, queues and load balancers connect to serve traffic. Here you drag those components onto a canvas, wire them together, start from templates such as URL Shortener or Chat Application, and export PNG, SVG or JSON.
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.
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.