System Design with Mermaid.js: Visualizing Architecture
Learn how to use Mermaid.js diagrams to document distributed system architectures — including sequence diagrams, flowcharts, and ER diagrams — embedded directly in Markdown.
Good architecture documentation lives alongside the code. Mermaid.js lets you write diagrams as text in Markdown, version them with Git, and render them automatically — no diagram tool accounts needed.
Request Lifecycle: Sequence Diagram
The following diagram shows how a typical API request flows through a layered system — from browser to database and back.
Microservices Architecture: Flowchart
This flowchart maps the service topology of an event-driven order processing system.
Database Schema: ER Diagram
A blog platform’s core entity-relationship model.
Why Diagrams-as-Code
| Approach | Version Control | Diff-friendly | Always in Sync |
|---|---|---|---|
| PNG/SVG exports | ✗ | ✗ | Manually |
| Draw.io XML | ✓ | Barely | Manually |
| Mermaid.js | ✓ | ✓ | Auto-renders |
Mermaid supports flowcharts, sequence diagrams, ER diagrams, Gantt charts, class diagrams, state machines, and more. Every diagram above lives in this Markdown file — no external tools, no stale screenshots.
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