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Developer Toolkit

Elixir & Phoenix Patterns

Master Elixir and Phoenix development with Cursor IDE and Claude Code. These patterns cover functional programming, OTP principles, LiveView, concurrent systems, and the unique features that make Elixir perfect for building fault-tolerant, real-time applications.

Quick Setup for Elixir Projects

Section titled “Quick Setup for Elixir Projects”

Initialize Elixir Project with AI

Section titled “Initialize Elixir Project with AI”
  1. Open Cursor in your workspace
  2. Launch Agent mode (Cmd/Ctrl + I)
  3. Prompt: “Create an Elixir Phoenix project with:
    • Phoenix 1.7+ with LiveView
    • Ecto for database
    • Tailwind CSS
    • Authentication system
    • Docker configuration
    • Test setup with ExUnit”
  4. Agent handles mix commands and setup

Phoenix Framework Patterns

Section titled “Phoenix Framework Patterns”

Application Architecture

Section titled “Application Architecture”
# Phoenix architecture prompt:
"Set up Phoenix application with:
- Contexts for domain logic
- LiveView for real-time UI
- PubSub for messaging
- Ecto schemas and migrations
- Background jobs with Oban
- Telemetry for monitoring"


# Generated structure:
lib/
  my_app/
    accounts/        # Context
    catalog/         # Context
    mailer/
    repo.ex
  my_app_web/
    live/
    controllers/
    components/
    router.ex

LiveView Development

Section titled “LiveView Development”

Interactive UI Components

Section titled “Interactive UI Components”
# LiveView component prompt:
"Create a LiveView for real-time dashboard with:
- Multiple chart components
- Live data updates via PubSub
- User interactions
- Optimistic UI updates
- Error recovery"

Real-Time Features

Section titled “Real-Time Features”
# Real-time features prompt:
"Implement real-time chat with:
- Phoenix Channels
- Presence tracking
- Message history
- Typing indicators
- Read receipts
- Push notifications"

LiveView Best Practices

AI can help with:

  • Optimizing assigns updates
  • Reducing data over wire
  • Client-side hooks
  • JavaScript interop
  • SEO considerations

OTP Patterns

Section titled “OTP Patterns”

GenServer Implementation

Section titled “GenServer Implementation”
# GenServer prompt:
"Create GenServer for:
- Rate limiting service
- State persistence
- Crash recovery
- Dynamic supervision
- Telemetry events
- Backpressure handling"

Supervision Trees

Section titled “Supervision Trees”
  1. Design Supervision: “Create supervision tree for payment processing”
  2. Implement Workers: “Add GenServer workers with restart strategies”
  3. Add Dynamic Supervisors: “Implement dynamic worker pools”
  4. Monitor Health: “Add telemetry and health checks”

Ecto Patterns

Section titled “Ecto Patterns”

Database Design

Section titled “Database Design”
# Ecto schema prompt:
"Design Ecto schemas for e-commerce:
- Multi-tenant architecture
- Polymorphic associations
- Soft deletes
- Audit logging
- Full-text search
- Database views"

Advanced Queries

Section titled “Advanced Queries”

Complex Queries 

# Prompt: "Create Ecto query with:
# - Window functions
# - CTEs
# - Lateral joins
# - Aggregations"

Performance 

# Prompt: "Optimize queries with:
# - Preloading strategies
# - Batch loading
# - Query fragments
# - Raw SQL when needed"

Concurrent Programming

Section titled “Concurrent Programming”

Process Design

Section titled “Process Design”
# Concurrency patterns prompt:
"Implement concurrent system for:
- Parallel data processing
- Task supervision
- Flow-based programming
- GenStage pipelines
- Broadway integration
- Back-pressure handling"

Actor Model

Section titled “Actor Model”
# Actor pattern:
"Design actor system with:
- Message protocols
- State machines
- Event sourcing
- Process registry
- Distributed actors"

Testing Strategies

Section titled “Testing Strategies”

Comprehensive Testing

Section titled “Comprehensive Testing”
# Test suite prompt:
"Create test suite with:
- Unit tests with ExUnit
- LiveView testing
- Channel testing
- Integration tests
- Property-based tests with StreamData
- Mox for mocking"

Test Patterns

Section titled “Test Patterns”
  1. Factory Setup: “Create test factories with ExMachina”
  2. Async Tests: “Configure async test execution”
  3. Database Sandboxing: “Set up Ecto sandbox mode”
  4. Coverage: “Add test coverage reporting”

Authentication & Security

Section titled “Authentication & Security”

Auth Implementation

Section titled “Auth Implementation”
# Auth system prompt:
"Implement authentication with:
- Pow or Guardian
- Multi-factor auth
- OAuth providers
- Session management
- Password policies
- Account lockout"

Security Patterns

Section titled “Security Patterns”

Security Checklist

AI can implement:

  • CSRF protection
  • Content Security Policy
  • Rate limiting
  • Input sanitization
  • SQL injection prevention
  • XSS protection

API Development

Section titled “API Development”

GraphQL with Absinthe

Section titled “GraphQL with Absinthe”
# GraphQL API prompt:
"Create GraphQL API with Absinthe:
- Schema design
- Resolvers with dataloader
- Subscriptions
- Authentication middleware
- Error handling
- Schema stitching"

REST API

Section titled “REST API”
# REST API design:
"Create JSON API with:
- Resource controllers
- Pagination
- Filtering
- API versioning
- OpenAPI docs"

Performance Optimization

Section titled “Performance Optimization”

Application Performance

Section titled “Application Performance”
# Performance optimization:
"Optimize Phoenix app for:
- Response time reduction
- Memory usage
- Database query optimization
- Caching strategies
- CDN integration
- Load testing"

Caching Strategies

Section titled “Caching Strategies”

ETS Caching 

# Prompt: "Implement ETS cache:
# - TTL support
# - Cache warming
# - Invalidation
# - Memory limits"

Redis Integration 

# Prompt: "Add Redis caching:
# - Connection pooling
# - Pub/sub support
# - Distributed cache
# - Cache aside pattern"

Deployment Patterns

Section titled “Deployment Patterns”

Release Management

Section titled “Release Management”
# Deployment prompt:
"Set up deployment with:
- Elixir releases
- Config providers
- Runtime configuration
- Health checks
- Rolling updates
- Kubernetes manifests"

Production Setup

Section titled “Production Setup”
  1. Build Release: “Configure mix release with Docker”
  2. Database Migrations: “Set up release migrations”
  3. Monitoring: “Add AppSignal or Telemetry”
  4. Scaling: “Configure clustering and service discovery”

Distributed Systems

Section titled “Distributed Systems”

Clustering

Section titled “Clustering”
# Distributed Elixir prompt:
"Implement distributed system with:
- libcluster for discovery
- Global process registry
- Distributed PubSub
- CRDTs for state
- Split-brain handling
- Network partitions"

Event Sourcing

Section titled “Event Sourcing”
# Event sourcing implementation:
"Create event-sourced system with:
- Commanded framework
- Event store
- Projections
- Process managers
- Saga orchestration
- Snapshot strategies"

Best Practices with AI

Section titled “Best Practices with AI”

Effective Elixir Prompts

Section titled “Effective Elixir Prompts”
# Structure prompts like:
"Create [module/function] in Elixir that:
- Follows OTP principles
- Handles these failure cases: [list]
- Includes @spec and @doc
- Has property-based tests
- Uses pattern matching effectively"

Code Quality

Section titled “Code Quality”

Advanced Patterns

Section titled “Advanced Patterns”

Metaprogramming

Section titled “Metaprogramming”
# Macro development:
"Create macro for:
- DSL implementation
- Compile-time validation
- Code generation
- AST manipulation
- Hygiene considerations"

Native Integration

Section titled “Native Integration”
# NIF/Port integration:
"Implement native integration:
- Rustler for NIFs
- Error handling
- Resource management
- Async NIFs
- Port drivers"

Common Pitfalls

Section titled “Common Pitfalls”

Avoid These Issues

When using AI for Elixir:

  • Don’t ignore OTP principles
  • Avoid mutable state patterns
  • Remember processes are cheap
  • Use supervisors appropriately
  • Test concurrent code thoroughly

Next Steps

Section titled “Next Steps”