perf-analysis

name	perf-analysis
description	Identify performance bottlenecks — slow queries, N+1 problems, unnecessary work, memory issues, and optimization opportunities. Trigger on /perf-analysis, or when investigating slow code, high latency, or resource usage.
user-invocable	true
allowed-tools	Read, Grep, Glob, Bash

Performance Analysis

Find and diagnose performance bottlenecks. Read-only analysis — do not optimize without verification.

Workflow

1. Identify the slow path

• What is the user-visible symptom? (slow page load, high CPU, memory growth, slow API)
• Trace the request/code path end-to-end.
• Look for obvious culprits: loops over large data, repeated DB calls, sync I/O.

2. Common anti-patterns

Database

• N+1 queries in loops.
• Missing indexes on filtered/joined columns.
• SELECT * when only a few columns are needed.
• Large result sets processed in memory.
• Slow GROUP BY / ORDER BY on unindexed columns.

Code

• Unnecessary work in hot paths (redundant computations, repeated lookups).
• Blocking I/O in async contexts.
• Large object allocations in tight loops.
• Inefficient data structures (array search instead of Set/Map).
• Recursion without depth limits.

Network

• Sequential API calls that could be parallel.
• Chatty protocols (many small requests instead of one batch).
• Large payloads with unnecessary data.
• No caching for repeated requests.
• Connection pooling issues.

Memory

• Objects retained longer than needed (closures, event listeners).
• Growing caches without eviction policy.
• Large strings/buffers held in memory.
• Stream processing vs loading everything at once.

3. Optimization rules

1. Measure first — never optimize without data. Profile or instrument.
2. One change at a time — change, measure, compare.
3. The 80/20 rule — 80% of gains come from 20% of the code. Find that 20%.
4. Know when to stop — diminishing returns. "Fast enough" is fine.
5. Document the trade-off — faster code is often less readable. Note why.

Experience Log

This skill learns from experience. Mechanism:

• Read .claude/experience/perf-analysis.md at skill start to benefit from past lessons.
• Write to .claude/experience/perf-analysis.md after use if you learned something new.
• Format: YYYY-MM-DD: <lesson> — one line per entry.
• Evolve: If the same issue repeats 3+ times, update this SKILL.md itself.