domain-driven-design
Expert guidance for Domain-Driven Design architecture and implementation. Use when designing complex business systems, defining bounded contexts, structuring domain models, choosing between modular monolith vs microservices, implementing aggregates/entities/value objects, or when users mention "DDD", "domain-driven design", "bounded context", "aggregate", "domain model", "ubiquitous language", "event storming", "context mapping", "domain events", "anemic domain model", strategic design, tactical patterns, or domain modeling. Helps make architectural decisions, identify subdomains, design aggregates, and avoid common DDD pitfalls.
What this skill does
# Domain-Driven Design Skill DDD manages complexity through alignment between software and business reality. **Strategic design (boundaries, language, subdomains) provides more value than tactical patterns (aggregates, repositories).** ## When to Apply DDD **Apply DDD when:** - Domain has intricate business rules - System is long-lived and high-value - Domain experts are available - Multiple teams/departments involved - Software represents competitive advantage **DDD is overkill when:** - Simple CRUD applications - Tight deadlines, limited budgets - No domain experts available - Complexity is purely technical, not business ## Core Workflow 1. Domain Discovery → 2. Bounded Context Definition → 3. Context Mapping → 4. Architecture Selection → 5. Tactical Implementation See [WORKFLOW.md](WORKFLOW.md) for detailed step-by-step instructions for each phase. ## Quick Reference ### Subdomain Types (Problem Space) | Type | Investment | Example | |------|-----------|---------| | **Core** | Maximum - competitive advantage | Recommendation engine, trading logic | | **Supporting** | Custom but quality tradeoffs OK | Inventory management | | **Generic** | Buy/outsource | Auth, email, payments | ### Key Decision: Entity vs Value Object - **Entity**: Has identity, tracked through time, mutable → `Customer`, `Order` - **Value Object**: Defined by attributes, immutable, interchangeable → `Money`, `Address`, `Email` **Default to value objects.** Only use entities when identity matters. ### Aggregate Design Rules (Vaughn Vernon) 1. Model true invariants in consistency boundaries 2. Design small aggregates (~70% should be root + value objects only) 3. Reference other aggregates by ID only 4. Use eventual consistency outside the boundary ### Architecture Decision ``` Start with modular monolith when: ├── Team < 20 developers ├── Domain boundaries unclear ├── Time-to-market critical └── Strong consistency required Consider microservices when: ├── Bounded contexts have distinct languages ├── Teams can own full contexts ├── Independent scaling required └── DevOps maturity exists ``` ## Detailed References - **Strategic Patterns**: See [references/STRATEGIC-PATTERNS.md](references/STRATEGIC-PATTERNS.md) for subdomains, bounded contexts, context mapping, event storming - **Tactical Patterns**: See [references/TACTICAL-PATTERNS.md](references/TACTICAL-PATTERNS.md) for entities, value objects, aggregates, services, repositories - **Architecture Alignment**: See [references/ARCHITECTURE-ALIGNMENT.md](references/ARCHITECTURE-ALIGNMENT.md) for clean/hexagonal architecture, modular monolith, microservices - **Workflow**: See [WORKFLOW.md](WORKFLOW.md) for detailed step-by-step DDD implementation process - **Anti-Patterns**: See [references/ANTI-PATTERNS.md](references/ANTI-PATTERNS.md) for common pitfalls and how to avoid them - **Examples**: See [EXAMPLES.md](EXAMPLES.md) for scenario walkthroughs applying DDD concepts - **Troubleshooting**: See [TROUBLESHOOTING.md](TROUBLESHOOTING.md) for common issues and solutions ## Critical Reminders 1. **Ubiquitous language first** - Code should read like business language 2. **Strategic before tactical** - Understand boundaries before implementing patterns 3. **Apply tactical patterns selectively** - Only in core domains where complexity warrants 4. **One aggregate per transaction** - Cross-aggregate consistency via domain events 5. **Persistence ignorance** - Domain layer has no infrastructure dependencies ## Related Skills | Need | Skill | |------|-------| | Data layer implementation | `spring-boot-data-ddd` — JPA/JDBC aggregates, repositories, transactions | | REST API layer | `spring-boot-web-api` — Controllers, validation, exception handling | | Module boundaries | `spring-boot-modulith` — Module structure, event-driven communication | | Testing patterns | `spring-boot-testing` — Aggregate tests, module tests, Scenario API | | Security for domains | `spring-boot-security` — Method-level authorization, role-based access |
Related in Design
contribute
IncludedLocal-only OSS contribution command center. Auto-refreshes the user's in-flight PR and issue state on invoke so conversations start with full context — no need to brief Claude on what's in flight. Helps the user find issues to contribute to on GitHub, builds per-repo dossiers of what each upstream expects (CLA, DCO, branch convention, AI policy, draft-first, review bots, issue templates), runs deterministic gates before any external action so AI-assisted contributions don't reach maintainers as slop. State is markdown-only: candidate files at ~/.contribute-system/candidates/, repo dossiers at ~/.contribute-system/research/, append-only event log at ~/.contribute-system/log.jsonl. No database, no cloud calls. Use when the user asks about their PRs / issues / contributions, wants to find new work to take on, claim an issue, build/refresh a repo's dossier, or draft a Design Issue or PR. Trigger with "/contribute", "what's my PR status", "find a contribution", "claim issue X", "draft a Design Issue for Y", "refresh dossier for Z".
architectural-analysis
IncludedUser-triggered deep architectural analysis of a codebase or scoped subtree across eight modes — information architecture, data flow, integration points, UI surfaces, interaction patterns, data model, control flow, and failure modes. This skill should be used when the user asks to "diagram this codebase," "map the architecture," "show the data flow," "give me an ERD," "trace control flow," "find the integration points," "verify the layout pattern," "audit the UX architecture," or any similar request whose primary deliverable is mermaid diagrams plus cited reports under docs/architecture/. Dispatches haiku/sonnet sub-agents in parallel for per-mode exploration, then verifies every citation mechanically before any node lands in a diagram. Not for one-off prose explanations of code (use code-explanation) or for high-level system design from scratch (use system-design).
mcp
IncludedModel Context Protocol (MCP) server development and tool management. Languages: Python, TypeScript. Capabilities: build MCP servers, integrate external APIs, discover/execute MCP tools, manage multi-server configs, design agent-centric tools. Actions: create, build, integrate, discover, execute, configure MCP servers/tools. Keywords: MCP, Model Context Protocol, MCP server, MCP tool, stdio transport, SSE transport, tool discovery, resource provider, prompt template, external API integration, Gemini CLI MCP, Claude MCP, agent tools, tool execution, server config. Use when: building MCP servers, integrating external APIs as MCP tools, discovering available MCP tools, executing MCP capabilities, configuring multi-server setups, designing tools for AI agents.
react-native-skia
IncludedDesign, build, debug, and optimise high-polish animated graphics in React Native or Expo using @shopify/react-native-skia, Reanimated, and Gesture Handler. Use when the user wants canvas-driven UI, shaders, paths, rich text, image filters, sprite fields, Skottie, video frames, snapshots, web CanvasKit setup, or performance tuning for custom motion-heavy elements such as loaders, hero art, cards, charts, progress indicators, particle systems, or gesture-driven surfaces. Also use when the user asks for fluid, glow, glass, blob, parallax, 60fps/120fps, or GPU-friendly animated effects in React Native, even if they do not explicitly say "Skia". Do not use for ordinary form/layout work with standard views.
plaid
IncludedProduct Led AI Development — guides founders from idea to launched product. Six capabilities: Idea (discover a product idea), Validate (pressure-test the idea against fatal flaws, problem reality, competition, and 2-week MVP feasibility), Plan (vision intake + document generation), Design (translate image references into a design.md spec), Launch (go-to-market strategy), and Build (roadmap execution). Use when someone says "PLAID", "plaid idea", "help me find an idea", "product idea", "idea from my business", "idea from my expertise", "plaid validate", "validate my idea", "pressure-test", "is this idea good", "find fatal flaws", "validate the problem", "plan a product", "define my vision", "generate a PRD", "product strategy", "plaid design", "design from image", "translate image to design", "create design.md", "extract design tokens", "plaid launch", "go-to-market", "launch plan", "GTM strategy", "launch playbook", "plaid build", "build the app", "start building", or "execute the roadmap".
nextjs-framer-motion-animations
IncludedAdds production-safe Motion for React or Framer Motion animations to Next.js apps, including reveal, hover and tap micro-interactions, whileInView, stagger, AnimatePresence, layout and layoutId transitions, reorder, scroll-linked UI, and lightweight route-content transitions. Use when the user asks to add, refactor, or debug Motion or Framer Motion in App Router or Pages Router codebases, especially around server/client boundaries, reduced motion, LazyMotion, bundle size, hydration, or route transitions. Avoid for GSAP-style timelines, WebGL or 3D scenes, heavy scroll storytelling, or CSS-only effects unless Motion is explicitly requested.