Laws of Software Engineering

Conway's Law

Organizations design systems that mirror their own communication structure.

Premature Optimization (Knuth's Optimization Principle)

Premature optimization is the root of all evil.

Hyrum's Law

With a sufficient number of API users, all observable behaviors of your system will be depended on by somebody.

The Boy Scout Rule

Leave the code better than you found it.

YAGNI (You Aren't Gonna Need It)

Don't add functionality until it is necessary.

Brooks's Law

Adding manpower to a late software project makes it later.

Gall's Law

A complex system that works is invariably found to have evolved from a simple system that worked.

The Law of Leaky Abstractions

All non-trivial abstractions, to some degree, are leaky.

Tesler's Law (Conservation of Complexity)

Every application has an inherent amount of irreducible complexity that can only be shifted, not eliminated.

CAP Theorem

A distributed system can guarantee only two of: consistency, availability, and partition tolerance.

Second-System Effect

Small, successful systems tend to be followed by overengineered, bloated replacements.

Fallacies of Distributed Computing

A set of eight false assumptions that new distributed system designers often make.

Law of Unintended Consequences

Whenever you change a complex system, expect surprise.

Zawinski's Law

Every program attempts to expand until it can read mail.

Dunbar's Number

There is a cognitive limit of about 150 stable relationships one person can maintain.

The Ringelmann Effect

Individual productivity decreases as group size increases.

Price's Law

The square root of the total number of participants does 50% of the work.

Putt's Law

Those who understand technology don't manage it, and those who manage it don't understand it.

Peter Principle

In a hierarchy, every employee tends to rise to their level of incompetence.

Bus Factor

The minimum number of team members whose loss would put the project in serious trouble.

Dilbert Principle

Companies tend to promote incompetent employees to management to limit the damage they can do.

Parkinson's Law

Work expands to fill the time available for its completion.

The Ninety-Ninety Rule

The first 90% of the code accounts for the first 90% of development time; the remaining 10% accounts for the other 90%.

Hofstadter's Law

It always takes longer than you expect, even when you take into account Hofstadter's Law.

Goodhart's Law

When a measure becomes a target, it ceases to be a good measure.

Gilb's Law

Anything you need to quantify can be measured in some way better than not measuring it.

Murphy's Law / Sod's Law

Anything that can go wrong will go wrong.

Postel's Law

Be conservative in what you do, be liberal in what you accept from others.

Broken Windows Theory

Don't leave broken windows (bad designs, wrong decisions, or poor code) unrepaired.

Technical Debt

Technical Debt is everything that slows us down when developing software.

Linus's Law

Given enough eyeballs, all bugs are shallow.

Kernighan's Law

Debugging is twice as hard as writing the code in the first place.

Testing Pyramid

A project should have many fast unit tests, fewer integration tests, and only a small number of UI tests.

Pesticide Paradox

Repeatedly running the same tests becomes less effective over time.

Lehman's Laws of Software Evolution

Software that reflects the real world must evolve, and that evolution has predictable limits.

Sturgeon's Law

90% of everything is crap.

Amdahl's Law

The speedup from parallelization is limited by the fraction of work that cannot be parallelized.

Gustafson's Law

It is possible to achieve significant speedup in parallel processing by increasing the problem size.

Metcalfe's Law

The value of a network is proportional to the square of the number of users.

DRY (Don't Repeat Yourself)

Every piece of knowledge must have a single, unambiguous, authoritative representation.

KISS (Keep It Simple, Stupid)

Designs and systems should be as simple as possible.

SOLID Principles

Five main guidelines that enhance software design, making code more maintainable and scalable.

Law of Demeter

An object should only interact with its immediate friends, not strangers.

Principle of Least Astonishment

Software and interfaces should behave in a way that least surprises users and other developers.

Dunning-Kruger Effect

The less you know about something, the more confident you tend to be.

Hanlon's Razor

Never attribute to malice that which is adequately explained by stupidity or carelessness.

Occam's Razor

The simplest explanation is often the most accurate one.

Sunk Cost Fallacy

Sticking with a choice because you've invested time or energy in it, even when walking away helps you.

The Map Is Not the Territory

Our representations of reality are not the same as reality itself.

Confirmation Bias

A tendency to favor information that supports our existing beliefs or ideas.

The Hype Cycle & Amara's Law

We tend to overestimate the effect of a technology in the short run and underestimate the impact in the long run.

The Lindy Effect

The longer something has been in use, the more likely it is to continue being used.

First Principles Thinking

Breaking a complex problem into its most basic blocks and then building up from there.

Inversion

Solving a problem by considering the opposite outcome and working backward from it.

Pareto Principle (80/20 Rule)

80% of the problems result from 20% of the causes.

Cunningham's Law

The best way to get the correct answer on the Internet is not to ask a question, it's to post the wrong answer.