Domain Driven Design

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

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.

DDD Deliverables Checklist

Use this checklist to keep DDD adoption practical and measurable.

Strategic deliverables

• Subdomain map (core, supporting, generic)
• Bounded context map and ownership
• Ubiquitous language glossary
• 1-2 ADRs documenting critical boundary decisions

Tactical deliverables

• Aggregate list with invariants
• Value object list
• Domain events list
• Repository contracts and transaction boundaries

Evented deliverables (only when required)

• Command and query separation rationale
• Event schema versioning policy
• Saga compensation matrix
• Projection rebuild strategy