investigating-code-patterns

name	Investigating Code Patterns
description	Systematically trace code flows, locate implementations, diagnose performance issues, and map system architecture. Use when understanding how existing systems work, researching concepts, exploring code structure, or answering "how/where/why is X implemented?" questions.

Investigating Code Patterns

When to Use This Skill

• Understanding how existing systems work end-to-end
• Researching concepts or technologies in your codebase
• Exploring code structure, patterns, and dependencies
• Answering "how/where/what" questions about implementations
• NOT for building new features (use implementation skills for that)

Core Investigation Types

1. Code Flow: "How does X work?"

Trace execution end-to-end from entry point to outcome.

Steps:

1. Find the entry point (API endpoint, component, function)
2. Trace function calls and data transformations
3. Follow imports and dependencies
4. Identify key decision points and error handling

2. Code Location: "Where is X implemented?"

Find where functionality lives in the codebase.

Steps:

1. Search for relevant keywords using grep
2. Check related files and modules
3. Identify main implementation and supporting files
4. Verify entry points and usage patterns

3. Performance Analysis: "Why is X slow?"

Diagnose bottlenecks using 3-phase approach.

Phase 1: Locate bottleneck

• Find entry point where slowness occurs
• Trace execution path
• Identify all operations (DB queries, API calls, compute, I/O)
• Look for obvious issues: N+1 queries, nested loops, large payloads

Phase 2: Root cause (if unclear)