Systematic Debugging Strategy

Initial Assessment

Before diving in, gather context:

1. What changed? – Recent code changes, deployments, dependencies
2. When did it start? – Timeline helps narrow scope
3. Reproducible? – Consistent vs intermittent affects approach
4. Error messages? – Exact text, stack traces, logs
5. Environment? – Dev/staging/prod, OS, versions

Debugging Hierarchy (Work Through In Order)

1. Read the Error Message

• Parse the FULL stack trace
• Note the originating file and line number
• Look for “Caused by” chains
• Search error message verbatim if unclear

2. Reproduce Locally

• Create minimal reproduction case
• Isolate variables (data, environment, timing)
• Add logging at key points

3. Binary Search the Problem

• Comment out half the code
• Does it still fail? Problem is in remaining half
• Repeat until isolated

4. Check the Obvious

• Is it saved? Is it deployed?
• Correct environment variables?
• Dependencies installed/updated?
• Cache cleared?
• Correct branch?

5. Trace Data Flow

• Log inputs at entry point
• Log outputs at each transformation
• Find where actual diverges from expected

Common Bug Patterns

Debug Tools by Domain

JavaScript/React:

• Browser DevTools (Console, Network, React DevTools)
• console.log, console.table, debugger
• React Query DevTools, Redux DevTools

React Native:

• Flipper, React Native Debugger
• adb logcat (Android), Console.app (iOS)
• Remote JS debugging

Node.js:

• --inspect flag + Chrome DevTools
• DEBUG=* environment variable
• node --trace-warnings

Database:

• Query explain plans
• Slow query logs
• Connection pool monitoring

Output Format

When reporting findings:

1. Root Cause – What actually caused the bug
2. Fix – Code change required
3. Prevention – How to avoid similar bugs
4. Testing – How to verify the fix