Rails Expert
Purpose
Provides expert Ruby on Rails development expertise specializing in Rails 7+ modern features, Hotwire stack (Turbo, Stimulus), and modern Rails patterns. Excels at building full-stack web applications with server-rendered HTML, real-time updates, and structured client-side behavior without heavy JavaScript frameworks.
When to Use
- Building modern Rails 7+ applications with Hotwire (Turbo, Stimulus)
- Implementing real-time features with Turbo Streams and Action Cable
- Migrating legacy Rails apps to modern Rails patterns and conventions
- Building API-first Rails applications with JSON:API or GraphQL
- Optimizing Rails application performance (database queries, N+1, caching)
- Implementing complex Rails patterns (Service Objects, Form Objects, Query Objects)
- Integrating Rails with modern frontend tools (Import Maps, esbuild, Vite)
Quick Start
Invoke this skill when:
- Building Rails 7+ apps with Hotwire/Turbo/Stimulus
- Implementing real-time features (Turbo Streams, Action Cable)
- Migrating legacy Rails to modern patterns
- Building API-first Rails (JSON:API, GraphQL)
- Optimizing performance (N+1, caching, eager loading)
- Using Rails patterns (Service Objects, Form Objects, Query Objects)
Do NOT invoke when:
- Only frontend development needed → Use frontend-developer or react-specialist
- Database-specific optimization → Use database-optimizer or postgres-pro
- Pure API design without Rails → Use api-designer
- DevOps/deployment only → Use devops-engineer
Core Capabilities
Rails 7+ Modern Features
- Hotwire: Turbo, Stimulus, and dynamic HTML updates without JavaScript frameworks
- Import Maps: JavaScript dependency management without build tools
- Rails 7 Action Text: Rich text editing with modern UI
- Encrypted Credentials: Enhanced security for sensitive data
- Async Query Loading: Improved database query performance
- Multi-DB Support: Primary/replica database configurations
- Parallel Testing: Faster test execution across processes
- Async Action Mailer: Non-blocking email delivery
Hotwire Stack
- Turbo Drive: Faster page navigation with automatic page caching
- Turbo Frames: Partial page updates without full reloads
- Turbo Streams: Real-time updates over WebSocket or SSE
- Stimulus Controllers: Structured client-side JavaScript behavior
- Turbo Morph: Smart DOM diffing for minimal re-renders
Modern Rails Patterns
- Service Objects: Extract business logic from controllers
- Query Objects: Complex database queries as reusable objects
- Form Objects: Handle complex form logic and validation
- Decorators: Presentational logic separation
- View Components: Reusable UI component architecture
- API Resources: Consistent API response formatting
Decision Framework
Rails Feature Selection
Rails Development Decision
├─ Need real-time updates
│ ├─ User-specific updates → Turbo Streams + Action Cable
│ ├─ Broadcast to multiple users → Action Cable channels
│ └─ Simple form responses → Turbo Streams over HTTP
│
├─ Frontend architecture
│ ├─ Minimal JS, server-rendered → Hotwire (Turbo + Stimulus)
│ ├─ Complex client-side logic → Rails API + React/Vue
│ └─ Hybrid approach → Turbo Frames for islands of interactivity
│
├─ Database strategy
│ ├─ Read-heavy workload → Multi-DB with read replicas
│ ├─ Complex queries → Query Objects + proper indexing
│ └─ Caching needed → Russian doll caching + fragment caching
│
└─ Code organization
├─ Fat models → Extract Service Objects
├─ Complex validations → Form Objects
└─ Business logic in controllers → Move to servicesPerformance Optimization Matrix
| Issue | Solution | Implementation |
|---|---|---|
| N+1 queries | Eager loading | includes(:association) / preload |
| Slow counts | Counter caches | counter_cache: true on associations |
| Repeated queries | Fragment caching | cache @object do blocks |
| Large datasets | Pagination | Kaminari / Pagy gems |
| Slow API responses | JSON caching | stale? / fresh_when |
Best Practices
Rails 7+ Features
- Hotwire First: Use Turbo/Stimulus before reaching for JS frameworks
- Import Maps: Manage JS dependencies without complex bundlers
- Async Query Loading: Leverage parallel query execution
- Multi-DB: Use read replicas for read-heavy workloads
Code Organization
- Service Objects: Extract business logic from controllers
- Query Objects: Encapsulate complex database queries
- Form Objects: Handle complex form validation logic
- View Components: Create reusable, testable UI components
Performance
- Eager Loading: Always use includes/preload for associations
- Counter Caches: Pre-calculate counts for associations
- Caching Strategy: Implement multi-level caching
- Database Indexes: Add indexes based on query patterns
Testing
- System Tests: Use for critical user journeys
- Component Tests: Test View Components in isolation
- Request Tests: Test API endpoints comprehensively
- Model Tests: Test business logic at unit level
Anti-Patterns
Architecture Anti-Patterns
- Fat Controllers: Business logic in controllers - use Service Objects and POROs
- Massive Models: Models handling too many responsibilities - extract concerns
- Callback Spaghetti: Complex callback chains - use service objects
- Skinny Controller, Fat Model: All logic in model - balance distribution
Database Anti-Patterns
- N+1 Queries: Not using eager loading - use includes/joins/preload
- Missing Indexes: Slow queries without proper indexes - analyze and add
- Counter Cache Miss: Repeated count queries - use counter caches
- Migrations Without Down: Non-reversible migrations - ensure reversibility
Performance Anti-Patterns
- Eager Loading Excess: Over-eager loading causing memory issues
- Missing Caching: No caching strategy - implement appropriate levels
- Render Bloat: Heavy view rendering - use fragments and caching
- Job Queue Backlog: No background job processing - use Active Job
Additional Resources
- Detailed Technical Reference: See REFERENCE.md
- Code Examples & Patterns: See EXAMPLES.md