Code Antipatterns

Top 10 Code Antipatterns

#	Antipattern	Category	Severity	One-Line Summary
1	Silent Failure	Surprise	Critical	Swallowing errors hides bugs until production
2	Mutable Shared State	Misuse	Critical	Shared mutation causes race conditions and data corruption
3	Primitive Obsession	Misuse	Warning	Using `String` where `EmailAddress` would prevent invalid data
4	Magic Values	Surprise	Warning	Unexplained literals obscure intent and invite inconsistency
5	God Object	Complexity	Warning	One class that knows and does everything
6	Premature Abstraction	Premature	Warning	Interfaces and factories before the second use case exists
7	Leaky Abstraction	Complexity	Warning	Callers must understand implementation details to use the API
8	Shotgun Surgery	Complexity	Warning	One logical change touches many files
9	Premature Optimization	Premature	Warning	Optimizing without profiling first
10	Cargo Cult Code	Premature	Note	Copying patterns without understanding why they exist

Severity	Meaning	Action	Examples
Critical	Active risk of data loss, security breach, or production failure	Fix immediately	Silent failure, mutable shared state
Warning	Ongoing cost in maintainability, reliability, or team velocity	Fix soon or create a ticket	God object, primitive obsession, magic values
Note	Code smell that may not warrant immediate action	Consider during refactoring	Cargo cult code, lava flow, boolean blindness

Signal	Antipattern	Acceptable Tradeoff
Duplicate code in two places	Wait — under threshold	Fix if three or more occurrences
Function takes a boolean param	Antipattern if unclear at call site	Acceptable if only one boolean and meaning is obvious
No interface for a dependency	Fine — add when second impl arrives	Antipattern if you need it for testing now
Global mutable state	Almost always an antipattern	Acceptable for true singletons (logger, config) with thread safety
Magic number	Antipattern if meaning is unclear	Acceptable for universally known values (0, 1, 100%)
Complex optimization	Antipattern without profiling evidence	Acceptable in measured hot paths with benchmarks
Dead code / commented blocks	Antipattern — delete it	Acceptable as temporary scaffold during active development
God object	Antipattern in production code	Acceptable in prototypes and spikes (plan to refactor)

Context	Lean Toward	Rationale
Prototype / spike	Tolerance — focus on validation	You'll rewrite anyway
Shared library / public API	Strict — fix misuse and surprise patterns	Consumers can't easily work around your mistakes
Hot path (measured)	Allow optimization complexity	Performance justifies readability tradeoff
Security boundary	Strict on all categories	Security antipatterns compound
Greenfield project	Moderate — invest in structure early	Foundation decisions compound over time
Legacy codebase	Prioritize critical severity only	Don't boil the ocean; fix what matters

No silent failures — errors either propagate or are explicitly handled
No magic values — all non-obvious literals are named constants
No unexpected side effects — query functions don't modify state
No mutable shared state without explicit thread safety
No primitive obsession — domain values have domain types where appropriate
No god objects — each class has a single clear responsibility
No premature abstraction — interfaces have or will soon have multiple implementations
No shotgun surgery — related logic is centralized

Situation	Action
Critical severity in production code	Fix now
Warning severity blocking current task	Fix now
Warning severity in adjacent code	Create a ticket
Note severity	Consider during next refactoring pass
Any severity in prototype/spike code	Note for later — don't gold-plate throwaway work