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Bug-Type Playbooks

Investigation focus and techniques by bug category.

Runtime Errors

Crashes, exceptions, uncaught errors.

Investigation focus:

Stack trace analysis (line, function, call chain)
Variable state at crash point
Input values that trigger crash
Environment differences (dev vs prod)

Common causes:

Null/undefined access
Type mismatches
Array out of bounds
Missing error handling
Resource exhaustion

Techniques:

Add try-catch with detailed logging
Validate assumptions with assertions
Check null/undefined before access
Log input values before processing

Logic Bugs

Wrong result, unexpected behavior.

Investigation focus:

Expected vs actual output comparison
Data transformations step by step
Conditional logic evaluation
State changes over time

Common causes:

Off-by-one errors
Incorrect comparison operators
Wrong order of operations
Missing edge case handling
State not reset between operations

Techniques:

Print intermediate values
Step through with debugger
Write test cases for edge cases
Check loop boundaries

Integration Failures

API, database, external service issues.

Investigation focus:

Request/response logging
Network traffic inspection
Authentication/authorization
Data format mismatches
Timing and timeouts

Common causes:

API version mismatch
Authentication token expired
Wrong content-type headers
Data serialization differences
Network timeout too short
Rate limiting

Techniques:

Log full request/response
Test with curl/httpie directly
Check API documentation version
Verify credentials and permissions
Monitor network timing

Intermittent Issues

Works sometimes, fails others.

Investigation focus:

What's different when it fails?
Timing dependencies
Shared state/resources
External conditions
Concurrency issues

Common causes:

Race conditions
Cache inconsistency
Clock/timezone issues
Resource contention
External service flakiness

Techniques:

Add timestamps to all logs
Run many times to find pattern
Check for async operations
Look for shared mutable state
Test under different loads

Performance Issues

Slow, memory leaks, high CPU.

Investigation focus:

Profiling and metrics
Resource usage over time
Algorithm complexity
Data volume scaling
Memory allocation patterns

Common causes:

N+1 queries
Inefficient algorithms
Memory leaks (unreleased resources)
Excessive allocations
Missing indexes
Unbounded caching

Techniques:

Profile with appropriate tools
Measure time/memory at checkpoints
Test with various data sizes
Check for cleanup in destructors
Monitor resource usage trends