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name: projection-patterns description: Build read models and projections from event streams. Use when implementing CQRS read sides, building materialized views, or optimizing query performance in event-sourced systems. metadata: aas-risk: safe aas-source: community aas-date-added: '2026-02-27'

Projection Patterns

Comprehensive guide to building projections and read models for event-sourced systems.

Use this skill when

• Building CQRS read models
• Creating materialized views from events
• Optimizing query performance
• Implementing real-time dashboards
• Building search indexes from events
• Aggregating data across streams

Do not use this skill when

• The task is unrelated to projection patterns
• You need a different domain or tool outside this scope

Instructions

• Clarify goals, constraints, and required inputs.
• Apply relevant best practices and validate outcomes.
• Provide actionable steps and verification.
• If detailed examples are required, open resources/implementation-playbook.md.

Resources

• resources/implementation-playbook.md for detailed patterns and examples.

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.