Agent skill

Projection Patterns

Covers building read models and materialized views from event streams in CQRS and event-sourced systems, including live, catch-up, persistent and inline projections.

MITAuto-check passedBackend & APIs

Install Projection Patterns

skills CLI

$ npx skills add wshobson/agents --skill projection-patterns -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install wshobson/agents projection-patterns --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/wshobson/agents.git skills-src && mkdir -p .claude/skills && cp -r skills-src/plugins/backend-development/skills/projection-patterns .claude/skills/projection-patterns && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Paste into Claude Code

Install the "projection-patterns" agent skill from https://github.com/wshobson/agents/tree/main/plugins/backend-development/skills/projection-patterns into .claude/skills/projection-patterns/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "projection-patterns", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/wshobson/agents/tree/main/plugins/backend-development/skills/projection-patterns

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add wshobson/agents --skill projection-patterns -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install wshobson/agents projection-patterns --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/wshobson/agents.git skills-src && mkdir -p .agents/skills && cp -r skills-src/plugins/backend-development/skills/projection-patterns .agents/skills/projection-patterns && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "projection-patterns" agent skill from https://github.com/wshobson/agents/tree/main/plugins/backend-development/skills/projection-patterns into .agents/skills/projection-patterns/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "projection-patterns", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add wshobson/agents --skill projection-patterns -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install wshobson/agents projection-patterns --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/wshobson/agents.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/plugins/backend-development/skills/projection-patterns .cursor/skills/projection-patterns && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "projection-patterns" agent skill from https://github.com/wshobson/agents/tree/main/plugins/backend-development/skills/projection-patterns into .cursor/skills/projection-patterns/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "projection-patterns", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/wshobson/agents.git --path plugins/backend-development/skills/projection-patterns

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add wshobson/agents --skill projection-patterns -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install wshobson/agents projection-patterns --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/wshobson/agents.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/plugins/backend-development/skills/projection-patterns .gemini/skills/projection-patterns && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "projection-patterns" agent skill from https://github.com/wshobson/agents/tree/main/plugins/backend-development/skills/projection-patterns into .gemini/skills/projection-patterns/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "projection-patterns", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install wshobson/agents projection-patterns

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add wshobson/agents --skill projection-patterns -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/wshobson/agents.git skills-src && mkdir -p .github/skills && cp -r skills-src/plugins/backend-development/skills/projection-patterns .github/skills/projection-patterns && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "projection-patterns" agent skill from https://github.com/wshobson/agents/tree/main/plugins/backend-development/skills/projection-patterns into .github/skills/projection-patterns/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "projection-patterns", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add wshobson/agents --skill projection-patterns -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install wshobson/agents projection-patterns --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/wshobson/agents.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/plugins/backend-development/skills/projection-patterns .opencode/skills/projection-patterns && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "projection-patterns" agent skill from https://github.com/wshobson/agents/tree/main/plugins/backend-development/skills/projection-patterns into .opencode/skills/projection-patterns/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "projection-patterns", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: projection-patterns
GitHub stars: 40k
Used in: 8 other repos
Token cost: ~565 tokens
SKILL.md length: 167 words
Files: 2 (incl. references)
Skills in repo: 142
Repo updated: Oct 5, 2026
First seen: Oct 7, 2026
Licence: MIT

At a glance

Covers building read models and materialized views from event streams in CQRS and event-sourced systems, including live, catch-up, persistent and inline projections.

Works in 2 steps: Projection Architecture → Projection Types
Building CQRS read models from an event store
SKILL.md covers When to Use This Skill, Core Concepts, Templates and detailed worked… and Best Practices
Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

This skill explains how projections turn an event store's stream into read models held in a database. It lays out the architecture as event store, projector and read model, and tabulates four projection types: live for real-time subscriptions, catch-up for replaying history, persistent for resuming from a stored checkpoint, and inline for updates in the same transaction as the write.

The practical rules are to make projections idempotent so replay is safe, store checkpoints, use transactions for multi-table updates, monitor lag, keep each projection independent, process events in order and denormalize for the queries you serve. Use cases include real-time dashboards, search indexes built from events and aggregations across streams. A references/details.md file holds templates.

When your agent uses it

Building CQRS read models from an event store
Rebuilding a read model from historical events
Feeding search indexes or dashboards from an event stream
Adding checkpoints and lag monitoring to projections

Example prompts

“Create a projector that builds an order summary table from our order events.”
“Make this projection idempotent so replaying events does not duplicate rows.”
“Add a catch-up projection to rebuild the customer dashboard from history.”

Workflow steps

2 steps, taken from the step headings in SKILL.md.

Projection Architecture
Projection Types

What it can do on your machine

Read from SKILL.md and the folder at commit 46891e7. It shows what the files ask for, not the result of running them.

Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Projection Patterns loads about 565 tokens when it runs, and up to ~4.1k if it reads all its reference files. Until then it costs about 50 tokens; SKILL.md has 167 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~50
When it runs · the whole SKILL.md, loaded when a task matches: ~565
With references · SKILL.md plus every file in references/, read only if the agent opens them: ~4.1k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from wshobson/agents at commit 46891e7, republished under its MIT licence (© wshobson). 167 words, ~565 tokens.

Download SKILL.mdSave it as .claude/skills/projection-patterns/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.

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.

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

Files

SKILL.md and 1 other file (references) in plugins/backend-development/skills/projection-patterns of wshobson/agents.

SKILL.md
references/details.md

Open the folder on GitHubat commit 46891e7

Used in 8 other repositories

We found 22 copies of this SKILL.md (exact, near-identical or edited) in other folders, from 8 other GitHub owners. This page covers the copy in wshobson/agents, which our catalogue first saw on October 7, 2026.

Compare with similar skills

Projection Patterns next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Projection Patterns compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
Projection Patterns this skillwshobson/agents	40k	8 repos	~565	Automated safety check: Pass	MIT	2 days ago
NestJS Modular Monolith Architecttech-leads-club/agent-skills	7k	—	~3.9k	Automated safety check: Pass	CC-BY-4.0	17 days ago
Microservices ArchitectJeffallan/claude-skills	12k	—	~1.8k	Automated safety check: Pass	MIT	4 days ago
Quarkus Patternsaffaan-m/ECC	274k	1 repos	~5.4k	Automated safety check: Pass	MIT	2 days ago
Architecture Selectionrsmdt/the-startup	536	—	~1.2k	Automated safety check: Pass	MIT	2 mo ago
Quarkus Patternsaffaan-m/ECC	274k	—	~6.1k	Automated safety check: Pass	MIT	2 days ago

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Questions about Projection Patterns

What does Projection Patterns do?

Covers building read models and materialized views from event streams in CQRS and event-sourced systems, including live, catch-up, persistent and inline projections. This skill explains how projections turn an event store's stream into read models held in a database. It lays out the architecture as event store, projector and read model, and tabulates four projection types: live for real-time subscriptions, catch-up for replaying history, persistent for resuming from a stored checkpoint, and inline for updates in the same transaction as the write.

When should I use Projection Patterns?

Projection Patterns fits situations like: building CQRS read models from an event store; rebuilding a read model from historical events; feeding search indexes or dashboards from an event stream; adding checkpoints and lag monitoring to projections.

How do I install Projection Patterns in Claude Code?

Run `npx skills add wshobson/agents --skill projection-patterns -a claude-code`. Or copy the skill folder (plugins/backend-development/skills/projection-patterns in wshobson/agents) into .claude/skills/projection-patterns in your project. Claude Code loads it when a task matches its description.

How do I install Projection Patterns in Codex?

Run `npx skills add wshobson/agents --skill projection-patterns -a codex`. Or copy the skill folder (plugins/backend-development/skills/projection-patterns in wshobson/agents) into .agents/skills/projection-patterns in your project. Codex loads it when a task matches its description.

Can I use Projection Patterns in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add wshobson/agents --skill projection-patterns -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/projection-patterns, .gemini/skills/projection-patterns, .github/skills/projection-patterns and .opencode/skills/projection-patterns in your project.

What does Projection Patterns need to run?

SKILL.md names no scripts, command-line tools or credentials: Projection Patterns is instructions for the agent only.

Does Projection Patterns access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Projection Patterns safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Projection Patterns use?

Projection Patterns is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Projection Patterns use?

About 565 tokens (SKILL.md is roughly 2.3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 3.6k tokens, read only when the agent opens those files.

What are the alternatives to Projection Patterns?

Skills that share tags, products or a category with Projection Patterns: NestJS Modular Monolith Architect (tech-leads-club/agent-skills, 7k stars), Microservices Architect (Jeffallan/claude-skills, 12k stars), Quarkus Patterns (affaan-m/ECC, 274k stars) and Architecture Selection (rsmdt/the-startup, 536 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Projection Patterns?

wshobson (a GitHub user) maintains it in wshobson/agents, which has 40,254 GitHub stars. The repository holds 142 skills in this directory. The repository was last updated on October 5, 2026.

Source: wshobson/agents on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install Projection Patterns

Facts

At a glance

What it does

When your agent uses it

Example prompts

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Projection Patterns

When to Use This Skill

Core Concepts

1. Projection Architecture

2. Projection Types

Templates and detailed worked examples

Best Practices

Do's

Don'ts

Files

Used in 8 other repositories

Compare with similar skills

Similar skills

More from wshobson/agents

Related

Questions about Projection Patterns