1. GATHER → Collect information, don't assume
   └─ Logs, metrics, user reports, timeline
2. REPRODUCE → Can you make the bug happen?
   ├─ Yes → Document exact steps
   └─ No → Analyze logs, check race conditions
3. ISOLATE → Where exactly does it fail?
   ├─ Frontend → Browser DevTools, React DevTools
   ├─ API → Network tab, API logs
   ├─ Backend → Laravel logs, dd(), dump()
   └─ Database → Query logs, slow queries
4. ANALYZE → Why does it fail? (Use 5 Whys/Fishbone)
   ├─ Ask "Why?" 5 times minimum
   ├─ Create causal chain
   └─ Identify contributing factors
5. FIX → Apply targeted fix (minimal change)
6. VERIFY → Confirm fix works without side effects
7. DOCUMENT → Blameless postmortem for learning

Problem: Users cannot log in

Why #1: Why can't users log in?
→ The authentication API returns 500 error

Why #2: Why does the API return 500?
→ Database connection timeout

Why #3: Why is there a connection timeout?
→ Connection pool exhausted

Why #4: Why is the pool exhausted?
→ Connections not being released after queries

Why #5: Why aren't connections released?
→ Missing finally block in database transaction code

ROOT CAUSE: Missing resource cleanup in transaction handling

                    ┌─ People (Developers/Users)
                    │   └─ Skills, Training, Communication
                    ├─ Process (Development/Deployment)
                    │   └─ Code review, Testing, CI/CD
                    ├─ Technology (Tools/Platforms)
PROBLEM ◄───────────┤   └─ Frameworks, Libraries, Infrastructure
                    ├─ Data (Input/Storage)
                    │   └─ Validation, Quality, Integrity
                    ├─ Environment (Runtime)
                    │   └─ Config, Dependencies, Resources
                    └─ External (Third-party)
                        └─ APIs, Services, Network

Problem: Checkout process fails intermittently

People:
├─ New developer unfamiliar with payment flow
└─ User enters invalid card format

Process:
├─ Missing integration tests for payment
└─ No retry logic in code review

Technology:
├─ Payment gateway timeout configuration
└─ Database connection pooling

Data:
├─ Stale shopping cart data
└─ Currency conversion precision

Environment:
├─ Different configs dev vs prod
└─ Memory pressure during peak

External:
├─ Payment gateway rate limiting
└─ Network latency spikes

              [System Outage]
                    │
                   OR
           ┌───────┴───────┐
           │               │
    [App Failure]   [Infra Failure]
           │               │
          OR              OR
      ┌───┴───┐       ┌───┴───┐
      │       │       │       │
   [OOM]  [Crash]  [DB Down] [Network]
      │       │       │
     AND     OR      OR
    ┌─┴─┐   ┌┴┐    ┌─┴─┐
    │   │   │ │    │   │
 [Leak][Traffic][Bug][Dep] [HW][Config]

1. **What happened?** 
   - Exact error message (copy-paste, screenshot)
   - What was the user trying to do?

2. **What should have happened?** 
   - Expected vs actual behavior

3. **When did it start?** 
   - Timestamp of first occurrence
   - After deployment? After specific action?
   - Pattern: Always? Sometimes? Specific time?

4. **Who is affected?**
   - All users? Specific users? Specific regions?
   - Can you reproduce it?

5. **What changed recently?**
   - Code deployments
   - Configuration changes
   - Infrastructure changes
   - Third-party updates

6. **Environment details?**
   - Browser/OS version
   - API version
   - Database state

# Recent commits - check what changed
git log --oneline -20
git log --since="2 days ago" --oneline

# Changes since last working state
git diff HEAD~5
git diff --stat HEAD~10

# Find commits that touched specific file
git log --oneline -p -- path/to/file

# Check deployment history
git tag --sort=-creatordate | head -10

# Current branch and uncommitted changes
git status
git stash list

| Time | Event | Source |
|------|-------|--------|
| 09:00 | Deployment v2.3.1 | CI/CD logs |
| 09:15 | First error reported | Sentry |
| 09:20 | Error rate spike to 5% | Monitoring |
| 09:25 | User complaints start | Support |
| 09:30 | Identified failing endpoint | APM |

Hypothesis: "Bug occurs when user has more than 100 items in cart"

Test Plan:
1. Create user with 50 items → Expected: Works
2. Create user with 100 items → Expected: Works
3. Create user with 101 items → Expected: Fails

Result: [CONFIRMED/REJECTED]

[User] → [Browser] → [Network] → [API Gateway] → [Backend] → [Database]
                                                      ↓
                                              [External Services]

For each layer, verify:
✓ Input is correct
✓ Processing is correct
✓ Output is correct

// Strategic console logging
console.group('[DEBUG] ComponentName');
console.log('Props:', props);
console.log('State:', state);
console.log('Context:', contextValue);
console.groupEnd();

// Network request debugging
console.log('[API Request]', { url, method, body });
console.log('[API Response]', { status, data, headers });

// React DevTools
// - Components tab: Inspect props, state, hooks
// - Profiler tab: Performance analysis

// Network tab checklist:
// ✓ Request URL correct?
// ✓ Request headers (Auth token present?)
// ✓ Request payload correct?
// ✓ Response status code
// ✓ Response body (actual data vs expected)
// ✓ Response time

// Status codes to investigate:
// 400 Bad Request → Check request payload
// 401 Unauthorized → Check auth token
// 403 Forbidden → Check permissions
// 404 Not Found → Check URL/routing
// 422 Validation Error → Check input data
// 429 Too Many Requests → Rate limiting
// 500 Internal Server Error → Check backend logs
// 502/503/504 → Infrastructure issues

// Quick debug (stops execution)
dd($variable);

// Dump without stopping
dump($variable);

// Log to file (storage/logs/laravel.log)
Log::debug('Checkpoint reached', ['data' => $data]);
Log::info('User action', ['user_id' => $user->id, 'action' => 'checkout']);
Log::warning('Potential issue', ['context' => $context]);
Log::error('Error occurred', ['exception' => $e->getMessage()]);

// Database query logging
DB::enableQueryLog();
// ... your code ...
$queries = DB::getQueryLog();
Log::debug('Queries executed', ['queries' => $queries]);

// Request debugging
Log::debug('Request details', [
    'url' => request()->fullUrl(),
    'method' => request()->method(),
    'input' => request()->all(),
    'headers' => request()->headers->all(),
    'user' => auth()->user()?->id,
]);

// Telescope (development) - visit /telescope
// Clockwork (browser extension)

-- Check slow queries
SHOW PROCESSLIST;

-- Analyze query performance
EXPLAIN ANALYZE SELECT * FROM orders WHERE user_id = 123;

-- Check for locks
SHOW OPEN TABLES WHERE In_use > 0;

-- Check indexes
SHOW INDEX FROM table_name;

-- Enable query logging (MySQL)
SET GLOBAL general_log = 'ON';
SET GLOBAL log_output = 'TABLE';
SELECT * FROM mysql.general_log ORDER BY event_time DESC LIMIT 50;

# Clear all caches
php artisan optimize:clear

# Specific cache clearing
php artisan config:clear
php artisan cache:clear
php artisan view:clear
php artisan route:clear

# Check routes
php artisan route:list
php artisan route:list --name=api
php artisan route:list --path=users

# Database commands
php artisan migrate:status
php artisan db:show

# Interactive debugging
php artisan tinker
>>> User::find(1);
>>> DB::table('orders')->where('status', 'pending')->count();

# Queue debugging
php artisan queue:failed
php artisan queue:retry all

# Clear cache and rebuild
rm -rf .next
npm run build

# Environment check
npx next info

# Bundle analysis
npm run build -- --analyze
# or
ANALYZE=true npm run build

# Find when bug was introduced (binary search)
git bisect start
git bisect bad HEAD
git bisect good v1.0.0
# Test, then: git bisect good/bad
git bisect reset

# Search commit messages
git log --grep="checkout" --oneline
git log --grep="fix" --oneline

# Find who changed a line
git blame path/to/file
git blame -L 10,20 path/to/file  # Lines 10-20

# Show what changed in a file over time
git log -p --follow -- path/to/file

# Find commits that changed specific code
git log -S "functionName" --oneline
git log -G "regex pattern" --oneline

# Laravel Telescope
# Visit: http://localhost:8000/telescope

# Database query analysis
# Enable in config/database.php
'mysql' => [
    'log_queries' => true,
]

# Application logs
tail -f storage/logs/laravel.log
# or with filtering
tail -f storage/logs/laravel.log | grep -i error

# Create a fix branch
git checkout -b fix/issue-description

# Document what you found
# Add comment in code explaining WHY, not just WHAT

- [ ] Fix addresses root cause, not just symptom
- [ ] No new bugs introduced
- [ ] Edge cases handled
- [ ] Error handling added
- [ ] Tests added/updated
- [ ] Documentation updated (if needed)
- [ ] Performance impact considered

- [ ] Original bug is fixed (tested with original steps)
- [ ] No new errors in console/logs
- [ ] Related features still work
- [ ] All tests pass
- [ ] Tested with edge cases
- [ ] Code review completed
- [ ] Tested in staging (if critical)
- [ ] Rollback plan ready

# Incident Postmortem: [Title]

**Date**: YYYY-MM-DD
**Severity**: Critical/High/Medium/Low
**Duration**: HH:MM
**Author**: [Name]
**Participants**: [Team members involved]

## Executive Summary
One paragraph summary for leadership/stakeholders.

## Timeline
| Time | Event |
|------|-------|
| HH:MM | First alert triggered |
| HH:MM | Team notified |
| HH:MM | Root cause identified |
| HH:MM | Fix deployed |
| HH:MM | Incident resolved |

## Impact
- Users affected: X
- Revenue impact: $Y (if applicable)
- Duration of degraded service: Z minutes

## Root Cause
Detailed explanation of the actual root cause.
Use 5 Whys or Fishbone diagram results here.

## What Went Well
- Quick detection
- Effective communication
- Fast rollback

## What Went Wrong
- Missing monitoring for X
- No automated test for Y
- Documentation outdated

## Action Items
| Action | Owner | Due Date | Status |
|--------|-------|----------|--------|
| Add monitoring for X | @person | YYYY-MM-DD | TODO |
| Write regression test | @person | YYYY-MM-DD | TODO |
| Update runbook | @person | YYYY-MM-DD | TODO |

## Lessons Learned
What can we do differently to prevent this class of issues?

## References
- Related incidents: #123, #456
- Relevant documentation links

□ What is the exact error message?
□ When did it start happening?
□ Can I reproduce it?
□ What changed recently? (git log)
□ Which layer is failing? (Frontend/API/Backend/DB)
□ Are there relevant logs?
□ Asked "Why?" at least 5 times?
□ Fix addresses root cause (not symptom)?
□ Tests added?
□ Postmortem documented?

# Laravel - Check what's happening
tail -f storage/logs/laravel.log
php artisan telescope:watch

# Clear everything
php artisan optimize:clear

# Database - Check for issues
php artisan migrate:status
php artisan db:show

# Git - What changed?
git log --oneline -10
git diff HEAD~3

# Rollback last migration
php artisan migrate:rollback

## Root Cause Analysis Report

### Issue Summary
[One paragraph: What happened, impact, duration]

### Investigation Steps
1. [Step 1: What was checked, what was found]
2. [Step 2: What was checked, what was found]
...

### 5 Whys Analysis
- Why #1: [Question] → [Answer]
- Why #2: [Question] → [Answer]
- Why #3: [Question] → [Answer]
- Why #4: [Question] → [Answer]
- Why #5: [Question] → [Answer]

### Root Cause
[The actual root cause - specific and actionable]

### Solution
[Fix applied or recommended]

### Prevention
[How to prevent recurrence]
- [ ] Action item 1
- [ ] Action item 2

### References
- Related logs/commits
- Documentation links