phx-perf

name	phx-perf
description	Analyze Elixir/Phoenix performance — N+1 queries, assign bloat, ecto optimization, genserver bottlenecks. Use when slowness, timeouts, or high memory reported.

Performance Analysis

Analyze code for performance issues across Ecto, LiveView, and OTP layers. Prioritize findings by impact and effort.

Usage

/skill:phx-perf                           # Analyze full project
/skill:phx-perf lib/my_app/accounts.ex    # Analyze specific module
/skill:phx-perf --focus ecto              # Ecto queries only
/skill:phx-perf --focus liveview          # LiveView memory only
/skill:phx-perf --focus otp               # OTP bottlenecks only

Arguments

$ARGUMENTS = Optional module/context path and --focus flag.

Iron Laws

1. MEASURE BEFORE OPTIMIZING — Never optimize without evidence of a problem
2. DATABASE FIRST — 90% of Elixir performance issues are query-related
3. ONE CHANGE AT A TIME — Isolate optimizations to measure impact
4. NEVER benchmark in dev mode — Always use MIX_ENV=prod for performance measurements; dev mode includes code reloading, debug logging, and unoptimized compilation that invalidate results

Workflow

Step 1: Identify Scope

Check specific file if provided. Otherwise scan full project:

# Find hot paths: contexts, LiveViews, workers
find lib/ -name "*.ex" | head -50

Step 2: Run Analysis Tracks

Spawn analysis agents in parallel based on focus:

Ecto Track (default or --focus ecto):

Spawn phx:elixir-reviewer with prompt: "Analyze for N+1 queries, missing preloads, unindexed queries, and inefficient patterns. Check: in loops, with Repo calls, missing , queries without indexes on WHERE/JOIN columns."