Domain Driven Design

---
name: domain-driven-design
description: "Plan and route Domain-Driven Design work from strategic modeling to tactical implementation and evented architecture patterns."
risk: safe
source: rootcastle-rei
tags: [ddd, domain, bounded-context, architecture]
---

# Domain-Driven Design

## Use this skill when

- You need to model a complex business domain with explicit boundaries.
- You want to decide whether full DDD is worth the added complexity.
- You need to connect strategic design decisions to implementation patterns.
- You are planning CQRS, event sourcing, sagas, or projections from domain needs.

## Do not use this skill when

- The problem is simple CRUD with low business complexity.
- You only need localized bug fixes.
- There is no access to domain knowledge and no proxy product expert.

## Instructions

1. Run a viability check before committing to full DDD.
2. Produce strategic artifacts first: subdomains, bounded contexts, language glossary.
3. Route to specialized skills based on current task.
4. Define success criteria and evidence for each stage.

### Viability check

Use full DDD only when at least two of these are true:

- Business rules are complex or fast-changing.
- Multiple teams are causing model collisions.
- Integration contracts are unstable.
- Auditability and explicit invariants are critical.

### Routing map

- Strategic model and boundaries: `@ddd-strategic-design`
- Cross-context integrations and translation: `@ddd-context-mapping`
- Tactical code modeling: `@ddd-tactical-patterns`
- Read/write separation: `@cqrs-implementation`
- Event history as source of truth: `@event-sourcing-architect` and `@event-store-design`
- Long-running workflows: `@saga-orchestration`
- Read models: `@projection-patterns`
- Decision log: `@architecture-decision-records`

If templates are needed, open `references/ddd-deliverables.md`.

## Output requirements

Always return:

- Scope and assumptions
- Current stage (strategic, tactical, or evented)
- Explicit artifacts produced
- Open risks and next step recommendation

## Examples

```text
Use @domain-driven-design to assess if this billing platform should adopt full DDD.
Then route to the right next skill and list artifacts we must produce this week.
```

## Limitations

- This skill does not replace direct workshops with domain experts.
- It does not provide framework-specific code generation.
- It should not be used as a justification to over-engineer simple systems.

---

> 🏰 **Rei Skills** — Curated by [Rootcastle Engineering & Innovation](https://www.rootcastle.com) | Batuhan Ayrıbaş  
> Engineering Beyond Boundaries | admin@rootcastle.com