10 Rules of Software Engineering

Conway’s Law

Also known as: “you will ship your org chart” and “any organization that designs a system will produce a design whose structure is a copy of the organization’s communication structure.” You may think you can avoid it via cross-functional standup meetings and stakeholder updates and decision matrices, but eventually and inevitably conflicting or diverging priorities will lead to equally conflicting or divergent processes and outcomes.

Brooks’s Law via The Mythical Man-Month

“Adding manpower to a late software project makes it later.” When you realize you’re not making the progress you thought you would and you’re management tries to reallocate resources from another part of the org, you’ll end up not only delaying the project, but you’ll likely ship a more brittle, more complex product.

Zawinsky’s Law

“Every program attempts to expand until it includes a web server. Those programs which cannot so expand are replaced by ones which can.” Today maybe: For web services, Zawinsky’s Law becomes “…until it requires a user account and collects all users’ data”; for physical devices, “…until it includes an insecure wifi access point with a default password you can’t change. And a web server”.

Parkinson’s Law

“Work expands so as to fill the time available for its completion.” If you don’t set a deadline, then the project will never be completed. This is why iterating on a minimum viable product within fixed timelines is important.

Pareto’s Fallacy

Pareto’s Principle is easy to misinterpret, especially by management, often leading to Pareto’s Fallacy: “When you’re 80% done, you think you only have 20% left.” The critical part that’s overlooked here is that those 20% will require 80% of your time.

Sturgeon’s Revelation

“90% of everything is crud.” Yes, including your products.

The Peter Principle

“In a hierarchy, every employee tends to rise to their level of incompetence. Thus, in time, every post tends to be occupied by an employee who is incompetent to carry out its duties.” Dunning and Kruger send their regards.

Eagleson’s Law

“Any code of your own that you haven’t looked at for six or more months might as well have been written by someone else.” 6 months is pretty optimistic.

Greenspun’s 10th Rule of Programming

Any custom developed authentication system contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Kerberos. This can be generalized to the Universal NIH-Rule: “Any custom developed system contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of the industry standard you refused to adopt”.

The Iceberg Fallacy

“The cost of development of a new software product is the only ~20% of the total cost of ownership (TOC) management sees and budgets for.”

Credits: https://www.indiehackers.com/8bit?id=WkCM4sc367MjAlaMcmMmgCR61k52

Bonus: The LGTM Dilemma

“If you want to quickly ship a 5 line code change, hide it in a 1500 line merge request.” (

Credits: @jansauer