AI-Powered Tool

System Design Generator

Transform requirements into comprehensive system design documents. Generate architecture diagrams, component specifications, API designs, and scalability strategies with AI.

AI Disclaimer

This AI tool is provided for informational and productivity purposes only. Output may be inaccurate and should be reviewed before use. Do not enter sensitive, confidential, or personal data. Your inputs are processed by third-party AI providers. Learn more about data handling

What is a System Design Generator?

A system design generator is an AI-powered tool that transforms your requirements into comprehensive technical architecture documents. Instead of spending days manually creating system design documentation, you describe what you need to build, and AI generates structured documentation including architecture patterns, component specifications, data flows, and scalability strategies.

This free AI system design tool is built for software architects, engineering leads, and development teams who need to create thorough technical documentation efficiently. Whether you’re preparing for an architecture review, planning a new system, or documenting existing infrastructure — well-structured system design documents ensure clarity and alignment. For product requirements, see the PRD Generator, and for agile work breakdown, try the Backlog Builder.

What Are System Design Documents?

A system design document (SDD) is a comprehensive technical specification that describes how a software system should be built. It serves as the blueprint for development teams, providing detailed information about architecture decisions, component interactions, and technical implementation strategies.

A well-crafted system design document answers critical questions:

  • What problem are we solving? The business requirements and technical constraints.
  • How is the system structured? The high-level architecture and component breakdown.
  • How do components interact? Data flows, APIs, and communication patterns.
  • How does it scale? Strategies for handling growth and increased load.
  • How is it secured? Authentication, authorization, and data protection.

System design documents bridge the gap between requirements and implementation, ensuring that everyone understands how the system will work before code is written.

Who is This Tool For?

Software Architects

You design systems at scale. This tool accelerates documentation creation, ensuring comprehensive coverage of architecture patterns, scalability strategies, and technical decisions. Spend less time writing documents and more time solving complex problems.

Engineering Leads and Tech Leads

You guide technical direction. Generate detailed system designs for new features or refactoring projects. Use the documentation for team alignment and stakeholder communication.

Senior Engineers

You make critical technical decisions. Create architecture proposals, compare design alternatives, and document your recommendations with professional-quality documentation.

System Designers

You plan infrastructure and integrations. Generate comprehensive specifications that cover databases, APIs, caching layers, and external service integrations. For database-specific designs, explore PostgreSQL integration with MCP or AWS infrastructure patterns.

Interview Candidates

You’re preparing for system design interviews. Practice by generating and studying various system architectures — from URL shorteners to distributed messaging systems. Use the Prompt Generator to craft optimal interview responses.

Technical Writers

You document technical systems. Use generated content as a starting point for user-facing documentation, reducing time spent on technical research.

How to Use This Tool

Getting started is straightforward. You can use Simple Mode for quick generation or Advanced Mode for detailed control:

  1. Describe your system — Write a clear description of what you need to build. Include the problem statement, expected scale, key features, and any constraints.

  2. Example input:

    Design a URL shortening service similar to bit.ly that:
1. Creates short URLs from long URLs
2. Redirects short URLs with minimal latency
3. Tracks click analytics
4. Supports 100M URLs created per month
5. Handles 10B redirects per month

99.9% availability required. Maximum redirect latency: 100ms.

  3. Select options — Choose detail level, scale, and which sections to include (API design, database, security, scalability).

  4. Generate — Click generate and get a complete system design document.

Advanced Mode (Full Control)

  1. System Name — Give your system a clear, descriptive identifier.

  2. Problem Statement — Describe the problem domain, business requirements, and success criteria.

  3. Functional Requirements — List specific features and capabilities the system must provide.

  4. Non-Functional Requirements — Specify performance, availability, latency, and other quality requirements.

  5. Constraints — Document technical limitations, budget constraints, or regulatory requirements.

  6. Existing Infrastructure — Describe current systems that the new design must integrate with.

  7. Select Options — Choose detail level, scale, and sections to include.

Understanding Document Sections

Overview Section

The executive summary of your system design. Includes:

  • Summary — High-level description of what the system does
  • Objectives — Key goals the system achieves
  • Scope — What’s included and excluded
  • Assumptions — Prerequisites and expectations
  • Constraints — Limitations affecting the design

Architecture Section

The core technical design explaining how components work together:

  • Architecture Style — Microservices, monolith, serverless, event-driven
  • Design Patterns — CQRS, event sourcing, saga, etc.
  • Component Relationships — How services communicate
  • Diagram Description — Textual representation for visualization

Components Section

Detailed breakdown of each system component:

  • Name and Type — Service, database, cache, queue, gateway
  • Technology — Specific tools and frameworks used
  • Responsibilities — What this component handles
  • Connections — Which other components it interacts with

Data Flow Section

How data moves through the system:

  • Request Flow — Step-by-step path of a typical request
  • Data Transformations — How data changes between components
  • Protocols — HTTP, gRPC, WebSocket, message queues

Database Section

Data storage design and strategy:

  • Database Type — PostgreSQL, MongoDB, DynamoDB, etc.
  • Schema Design — Table structures and relationships
  • Indexes — Query optimization strategies
  • Estimated Size — Storage projections

API Design Section

Interface specifications for the system:

  • API Style — REST, GraphQL, gRPC
  • Endpoints — Available operations with methods and paths
  • Authentication — How clients authenticate
  • Rate Limiting — Protection against abuse

Security Section

Protection strategies organized by category:

  • Authentication — Identity verification
  • Authorization — Access control
  • Encryption — Data protection at rest and in transit
  • Network Security — Firewall rules, VPCs
  • Compliance — Regulatory requirements

Scalability Section

Growth strategies for handling increased load:

  • Horizontal Scaling — Adding more instances
  • Vertical Scaling — Increasing instance capacity
  • Caching — Reducing database load
  • Sharding — Distributing data across nodes
  • Load Balancing — Distributing traffic

Deployment Section

How the system is deployed and operated:

  • Deployment Strategy — Blue-green, canary, rolling
  • Infrastructure — Cloud services and resources
  • CI/CD — Build and deployment pipelines
  • Environments — Development, staging, production

Monitoring Section

Observability and operational health:

  • Metrics — Key performance indicators to track
  • Alerting — Conditions that trigger notifications
  • Logging — Log aggregation strategy
  • Tracing — Distributed request tracing

Understanding Scale Levels

Small (1K-10K Users)

Best for MVPs, internal tools, and early-stage startups:

  • Single region deployment
  • Simpler architecture patterns
  • Fewer redundancy requirements
  • Focus on functionality over scale

Medium (10K-100K Users)

The growth stage requiring more sophistication:

  • Multi-AZ deployment for high availability
  • Introduction of caching layers
  • Load balancing requirements
  • Database read replicas

Large (100K-1M Users)

Significant scale requiring distributed systems:

  • Multi-region considerations
  • Advanced caching strategies
  • Database sharding options
  • CDN integration

Enterprise (1M+ Users)

Global scale with stringent requirements:

  • Global distribution
  • Complex partitioning strategies
  • Advanced observability
  • Regulatory compliance across jurisdictions

Understanding Detail Levels

Basic

High-level overview suitable for initial discussions:

  • Key components and their purposes
  • Primary data flows
  • Core architecture decisions
  • ~60 second generation time

Use when: Initial brainstorming, executive presentations, quick feasibility assessments.

Standard

Balanced detail for most engineering needs:

  • Detailed component specifications
  • API endpoint designs
  • Database schema outlines
  • Security considerations
  • ~90 second generation time

Use when: Sprint planning, architecture reviews, technical proposals.

Comprehensive

Full specification for critical systems:

  • Extensive component documentation
  • Complete API specifications
  • Detailed security analysis
  • Cost estimates
  • Implementation timelines
  • ~120 second generation time

Use when: Production system planning, compliance documentation, architecture approvals.

Export Formats

Markdown (.md)

Best for documentation, wikis, and version control:

  • Confluence or Notion documentation
  • GitHub/GitLab wikis
  • Pull request descriptions
  • Technical blogs

JSON (.json)

Best for programmatic access and integrations:

  • Architecture tooling
  • CI/CD pipelines
  • Custom visualization tools
  • Data analysis

Mermaid Diagrams

Best for visual documentation:

  • Architecture diagrams
  • Sequence diagrams
  • Component relationships
  • Embedded in Markdown

AI Provider Options

To understand the differences between AI providers and models, see the guide on understanding the AI landscape:

Google Gemini (Default)

Uses our server-side Gemini integration. No setup required. Learn more about how LLMs power these tools.

Best for: Getting started quickly, consistent results, no API key needed.

OpenRouter (Free Models)

Access various free AI models through OpenRouter.

Current free models:

  • Google Gemma 3 1B/4B
  • Meta Llama 3.2 3B Instruct
  • Mistral Small 3.1 24B
  • Qwen3 14B

Best for: Trying different models, cost-sensitive usage.

Bring Your Own Key (BYOK)

Use your own API keys with Gemini or OpenRouter. Your API key goes directly to the provider — it never touches our servers.

Best for: Heavy usage, privacy requirements, specific model preferences.

Tips for Better Results

Be Specific About Scale

Weak input:

Design a chat application

Strong input:

Design a real-time chat application that:
- Supports 1M concurrent users
- Delivers messages within 100ms
- Stores message history for 7 years
- Supports file sharing up to 100MB
- Includes read receipts and typing indicators

Include Non-Functional Requirements

Instead of just listing features, specify quality attributes:

Non-Functional Requirements:
- 99.99% availability SLA
- P99 latency < 50ms for API calls
- Support 10,000 requests per second peak
- Recovery time objective (RTO): 1 hour
- Recovery point objective (RPO): 5 minutes

Specify Constraints

Help the AI make appropriate tradeoffs:

Constraints:
- Must use existing AWS infrastructure
- Budget: $50K/month for infrastructure
- Team: 5 backend engineers
- Timeline: 3 months to MVP
- Must comply with GDPR and SOC 2

Common System Design Patterns

URL Shortener

Classic interview problem demonstrating:

  • Base62 encoding for short codes
  • Caching for high read:write ratio
  • Database partitioning strategies

Rate Limiter

Essential for API protection:

  • Token bucket algorithm
  • Sliding window counters
  • Distributed rate limiting with Redis

Distributed Message Queue

Event-driven architecture foundation:

  • Message partitioning
  • Consumer group management
  • At-least-once vs exactly-once delivery

Notification System

Multi-channel communication:

  • Push notification gateways
  • Email delivery optimization
  • Rate limiting per user

Search System

Full-text search at scale:

  • Inverted indexes
  • Relevance scoring
  • Index sharding strategies

Frequently Asked Questions

How accurate are the generated designs?

The AI generates high-quality system designs based on industry best practices. The accuracy depends on how well you describe your requirements. We recommend always reviewing and customizing generated documents for your specific context.

Can I regenerate with different options?

Yes! You can modify your input, change detail level, enable/disable sections, and regenerate as many times as needed.

Are my inputs stored?

Your inputs are processed for generation only. We don’t store your proprietary requirements. BYOK mode sends data directly to your chosen provider.

Can I edit the generated documents?

Currently, you can export and edit in your preferred tool. Direct in-browser editing is planned for a future update.

How many designs can I generate per day?

Anonymous users get 3 generations per day, free logged-in users get 10 per day. BYOK users have unlimited access.

Making the Most of Generated Designs

Use as a Starting Point

AI-generated system designs provide structure and coverage. Add your specific context, organizational patterns, and domain expertise.

Iterate and Refine

Generate multiple versions with different scale levels. Combine the best elements from each. Test different requirement framings.

Share and Collaborate

Use generated documents as conversation starters with your team. Stakeholder feedback will strengthen the design significantly.

Version Control

Store system design documents alongside code. Track changes over time and maintain alignment between documentation and implementation.

Your system deserves thoughtful architecture. Start generating system design documents now.