Perfection Considered Harmful

People are always making mistakes. People send emails to the wrong person, or forget an attachment. They give you the wrong change at the checkout or bump into you in the street. Every day, people make little mistakes. For the most part we’re quite forgiving of each other. We understand that the other human being we’re looking at is doing their best and as long as they try to fix things quickly we cut them a bit of slack. But our forgiving nature is based on our ability to relate to the person who’s made the mistake as being like us, a fellow human being. We are notably less forgiving when someone is diving and needs to switch lanes before their junction. On the road, it is not a fellow human being who’s made a mistake, it’s “some idiot in a BMW”.

When it comes to software systems we are even less likely to relate to the person who’s made them. All software is designed, written and tested by people, but we don’t see it like that. We think of software as some alien entity that arrived on planet Earth fully formed. And like the evil BMW who wants to get in front of us, any mistakes that it makes are utterly unreasonable.

Within the software development world, we prevent mistakes by having people check things. Designs are reviewed, code is tested, the content of those tests are themselves reviewed, code is deployed to small groups of people first and monitored carefully, the list of things that went wrong is reviewed and fixes are made, tested, reviewed again, and then finally released to more people. If all goes well it will work perfectly and nobody who uses it will ever experience a problem.

All, never goes well.

Each layer of testing and checking is done by people, and people make mistakes. Each layer of checking just reduces the probability of a mistake getting through, but no amount of checking ever guarantees that the software is perfect. Playing the lottery every week will increase your chances of winning, but there’s no magic number of weeks you need to play before you’re guaranteed a jackpot. What is more, like playing the lottery, each time you get someone to check something it costs you money.

As a supplier of software to others, your job is to find the right balance when customers demand new features, developed quickly, with no bugs, on a budget. The cost of checking and re-checking each new bit of code that goes out the door must be traded off against the value of the new features you’re developing. If you had the new feature 3 weeks earlier, but had to refund 3 customers who found errors in it, would that be worth it? Or does the cost of having 3 angry customers outweigh the benefit of getting the feature sooner?

There is no easy answer here. Be assured; the site will not stay up 100% of the time, there will be bugs, occasionally a sale will be lost or a refund will have to be made. This is a natural consequence of having human beings do work for you. But the important thing to remember is; do not allow people to think its reasonable to expect perfection. Involve the customers/users in the trade off decision making process. Try to put a human face on the software you’ve created. Be present as much as possible. Smile. Talk in terms of probabilities.  Be humble. Say “sorry” early when things go wrong. And if you do that really well, you may actually go up in people’s minds when things go wrong, not down.