elixir-review

Elixir / Phoenix Code Review

When to Use

• Reviewing Elixir code (Phoenix, OTP, GenServer, LiveView)
• Evaluating fault tolerance patterns (supervision trees)
• Real-time system review (WebSocket, PubSub)
• Concurrency and scalability assessment

Review Checklist

OTP Patterns

• Supervision trees properly structured (one_for_one, rest_for_one)
• GenServers have clear purpose (not catch-all)
• handle_info handles unexpected messages gracefully
• Timeouts configured for long-running GenServers
• Process registry used (not PID passing)
• ETS tables for read-heavy shared state

Phoenix Best Practices

• Contexts separate business logic from web layer
• Schemas define changesets with validation
• Controllers are thin (delegate to context)
• Plugs for cross-cutting concerns (auth, logging)
• Ecto queries composed (not raw SQL unless necessary)
• Background jobs via Oban (not raw Task.async)

Phoenix LiveView

• handle_event functions are small and focused
• assign used for all state (no process dictionary)
• phx-throttle/phx-debounce on frequent events
• PubSub for real-time updates across users
• Dead views implement mount/3 with proper assigns
• live_redirect vs push_patch used correctly

Elixir Best Practices

• Pattern matching over if/else chains
• Pipe operator (|>) for data transformations
• with for multi-step operations with error handling
• @spec type specs on public functions
• @doc documentation on public functions
• Structs for domain entities (not naked maps)
• Guards for function clause selection
• Enum and Stream used appropriately (eager vs lazy)

Concurrency

• Tasks supervised (not fire-and-forget)
• GenServer state doesn't grow unbounded
• Message queue monitored (Process.info for mailbox)
• Backpressure implemented for high-throughput
• Database connection pool sized correctly