Design Documents
Create detailed technical designs with Design Docs
Design Documents
Design Docs are comprehensive technical documents that describe the detailed design of a significant feature or system.
What is a Design Doc?
A Design Doc is a thorough document that:
- Details the complete technical design
- Guides implementation decisions
- Serves as a reference during development
- Documents the system for future maintenance
Design Docs are more detailed than ADRs or RFCs. They're intended to be the complete blueprint for implementation.
When to Write a Design Doc
Write a Design Doc when:
- ✅ Building a complex new feature
- ✅ Redesigning an existing system
- ✅ Creating a new service or component
- ✅ Making changes that span multiple teams
- ✅ Building something that will need long-term maintenance
Design Doc Structure
A comprehensive Design Doc includes:
Title & Metadata
- Document title
- Author(s)
- Reviewers
- Status and dates
Overview
Brief summary of what's being designed (1-2 paragraphs).
Goals & Non-Goals
Explicitly state:
- What this design aims to achieve
- What's explicitly out of scope
Background
Context needed to understand the design:
- Current system state
- Related systems
- Previous decisions
High-Level Design
Architecture overview:
- System components
- Data flow
- Key interactions
Include diagrams!
Detailed Design
In-depth specifications:
- API definitions
- Data models
- Algorithm details
- Error handling
Security Considerations
- Authentication/authorization
- Data protection
- Potential vulnerabilities
Testing Strategy
- Unit testing approach
- Integration testing
- Performance testing
Deployment Plan
- Rollout strategy
- Feature flags
- Rollback plan
Monitoring & Observability
- Metrics to track
- Alerting strategy
- Logging requirements
Timeline & Milestones
- Implementation phases
- Dependencies
- Estimated completion
Example Design Doc
# Design Doc: Real-time Collaboration System
**Author**: Jane Developer
**Reviewers**: John Architect, Sarah Security
**Status**: In Progress
**Last Updated**: February 2026
## Overview
This document describes the design for adding real-time
collaboration to the ArchDoc document editor, allowing
multiple users to edit documents simultaneously.
## Goals
- Enable multiple users to edit the same document
- Show presence indicators (who's viewing/editing)
- Display cursors and selections of other users
- Maintain document consistency across clients
## Non-Goals
- Offline editing (future work)
- Conflict resolution UI (auto-resolve only)
- Mobile app support (web only)
## Background
Currently, ArchDoc uses optimistic locking for edits.
When two users edit simultaneously, the second save
fails. This leads to a poor user experience.
Related systems:
- TipTap editor (current)
- NextAuth authentication
- Prisma database layer
## High-Level Design┌─────────────┐ WebSocket ┌────────────────┐ │ Client A │◄──────────────►│ Collab Server │ └─────────────┘ │ (Hocuspocus) │ │ │ ┌─────────────┐ WebSocket │ ┌────────┐ │ │ Client B │◄──────────────►│ │ Yjs │ │ └─────────────┘ │ │ CRDT │ │ │ └────────┘ │ └───────┬────────┘ │ ▼ ┌───────────────┐ │ Database │ │ (Persistence)│ └───────────────┘
### Components
1. **Yjs CRDT**: Conflict-free replicated data type
2. **Hocuspocus**: WebSocket server for Yjs
3. **TipTap Collaboration**: Editor integration
## Detailed Design
### WebSocket Protocol
[Detailed protocol specification...]
### Data Model Changes
[Schema updates...]
### API Endpoints
[New endpoints...]
## Security Considerations
- Authenticate WebSocket connections via JWT
- Validate company membership for document access
- Rate limit connection attempts
## Testing Strategy
1. Unit tests for CRDT operations
2. Integration tests with multiple clients
3. Load testing with 50 concurrent users
## Deployment Plan
1. Phase 1: Deploy collab server (feature flagged)
2. Phase 2: Enable for internal testing
3. Phase 3: Gradual rollout by company
4. Phase 4: General availability
## Timeline
- Week 1-2: Server implementation
- Week 3-4: Client integration
- Week 5: Testing and fixes
- Week 6: RolloutBest Practices
Include Diagrams
- Architecture diagrams
- Sequence diagrams
- Data flow diagrams
Use Excalidraw or Mermaid for diagrams.
Be Specific
- Include actual API schemas
- Define data models precisely
- Specify error cases
Consider Edge Cases
- What happens during failures?
- How do we handle partial states?
- What are the limits?
Get Early Feedback
- Share drafts with key stakeholders
- Iterate before full review
- Address concerns early
Update as You Go
- Design Docs are living documents
- Update when implementation differs
- Note changes and reasons
Creating a Design Doc in ArchDoc
- Navigate to Dashboard > Documents
- Click New Document
- Select Design Doc as the document type
- Enter a descriptive title
- Write your detailed design
- Add diagrams as needed
- Request sign-offs from stakeholders
- Update throughout implementation