Projection patterns

Skill FridrichMethod/awesome-skills/skills/projection-patterns

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.From its SKILL.md

Install

npx -y skills add FridrichMethod/awesome-skills --skill projection-patterns

Assembled from the repository path, not quoted from the project. Check it against their README if it does not work.

2 things to look at

no licenseNo license file was found in the repository. Code published without one is not open source by default, so using it at work is a question for whoever answers licensing questions where you are.
13 stars13 stars. Stars are a popularity signal and not a quality one, but at this level it is likely that nobody has read this closely except its author, and you would be relying on your own review.

SKILL.md

2.6 KB, 508 tokens by cl100k_base, as published. Nobody here has run it

Projection Patterns

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

When to Use This Skill

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

Core Concepts

1. Projection Architecture

┌─────────────┐     ┌─────────────┐     ┌─────────────┐
│ Event Store │────►│ Projector   │────►│ Read Model  │
│             │     │             │     │ (Database)  │
│ ┌─────────┐ │     │ ┌─────────┐ │     │ ┌─────────┐ │
│ │ Events  │ │     │ │ Handler │ │     │ │ Tables  │ │
│ └─────────┘ │     │ │ Logic   │ │     │ │ Views   │ │
│             │     │ └─────────┘ │     │ │ Cache   │ │
└─────────────┘     └─────────────┘     └─────────────┘

2. Projection Types

Type	Description	Use Case
Live	Real-time from subscription	Current state queries
Catchup	Process historical events	Rebuilding read models
Persistent	Stores checkpoint	Resume after restart
Inline	Same transaction as write	Strong consistency

Templates and detailed worked examples

Full template library and detailed worked examples live in references/details.md. Read that file when you need the concrete templates.

Best Practices

Do's

Make projections idempotent - Safe to replay
Use transactions - For multi-table updates
Store checkpoints - Resume after failures
Monitor lag - Alert on projection delays
Plan for rebuilds - Design for reconstruction

Don'ts

Don't couple projections - Each is independent
Don't skip error handling - Log and alert on failures
Don't ignore ordering - Events must be processed in order
Don't over-normalize - Denormalize for query patterns

What ships with it: 1 file

13.9 KB alongside SKILL.md

references/

details.md13.9 KB