Best for
- Building CQRS read models
- Creating materialized views from events
- Optimizing query performance
Source profileQuality 71/100
wshobson/agents/plugins/backend-development/skills/projection-patterns/SKILL.md
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.
- Source repository stars
- 38,313
- Declared platforms
- 0
- Static risk flags
- 1
- Last source update
- 2026-07-22
- Source checked
- 2026-07-28
Decision brief
What it does—and where it fits
Comprehensive guide to building projections and read models for event-sourced systems.
Not for
- Tasks that require unconfirmed production actions or broad system permissions.
- Environments where the pinned source and install steps cannot be inspected.
Compatibility matrix
Platform support, with evidence labels
| Platform | Status | Evidence | What to check |
|---|---|---|---|
| Codex | Not declared | No explicit evidence | Portability before use |
| Claude Code | Not declared | No explicit evidence | Portability before use |
| Cursor | Not declared | No explicit evidence | Portability before use |
| Gemini CLI | Not declared | No explicit evidence | Portability before use |
Installation
Inspect first. Install second.
The source command is displayed only when detected. A safe inspection prompt is always available so your agent can explain every action before execution.
Source-detected install commandSource
npx skills add https://github.com/wshobson/agents --skill "plugins/backend-development/skills/projection-patterns"Safe inspection promptEditorial
Inspect the Agent Skill "projection-patterns" from https://github.com/wshobson/agents/blob/c4b82b0ad771190355eb8e204b1329732a18449a/plugins/backend-development/skills/projection-patterns/SKILL.md at commit c4b82b0ad771190355eb8e204b1329732a18449a. List every install step, command, network request, credential, file read/write, external action, and rollback step. Explain whether it fits my task. Do not install or execute anything until I approve.
Workflow
What the source asks the agent to do
- 01
When to Use This Skill
Building CQRS read models
Building CQRS read modelsCreating materialized views from eventsOptimizing query performance - 02
Core Concepts
Review the “Core Concepts” section in the pinned source before continuing.
Review and apply the “Core Concepts” source section. - 03
1. Projection Architecture
Review the “1. Projection Architecture” section in the pinned source before continuing.
Review and apply the “1. Projection Architecture” source section. - 04
2. Projection Types
Review the “2. Projection Types” section in the pinned source before continuing.
Review and apply the “2. Projection Types” source section.
Permission review
Static risk signals and limitations
Reads files
The documentation asks the agent to read local files, directories, or repositories.
Full template library and detailed worked examples live in `references/details.md`. Read that file when you need the concrete templates.Evidence record
Why each signal appears
EvidenceSourceComputedTestedEditorial
| Signal | Value | Evidence type | Meaning |
|---|---|---|---|
| Quality score | 71/100 | Computed | Documentation, specificity, maintenance, and trust rules |
| Repository stars | 38,313 | Source | Repository attention, not individual Skill quality |
| Compatibility | 0 platforms | Source | Declared in the catalog source record |
| Usage guide | automated source guide | Editorial | Generated or reviewed according to the visible evidence level |
Pinned source
Provenance and original SKILL.md
- Repository
- wshobson/agents
- Skill path
- plugins/backend-development/skills/projection-patterns/SKILL.md
- Commit
- c4b82b0ad771190355eb8e204b1329732a18449a
- License
- MIT
- Collected
- 2026-07-28
- Default branch
- main
View the original SKILL.md
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