Have you ever wondered why, well of course you do. That’s what you do for living anyway. You develop one prototype and deploy it on your specially configure machine. Once it’s done and ready for audience, you carry out your prototype on another machine which you configure the same way with your private machine. Certain thing goes wrong surely but it’s nothing because you know what to do.
Different case is that the prototype is now no longer prototype. It’s a working instance used for production set on online and real time machine. People are now interacting with your work and to put it on sleep is not an option. You are tasked to make a small changes and you do it assuming the work and environment on which you deploy are still the same.
Sadly, they are not and now you are screwed. The work you have done diligently is now working no more. You suspect of change in environment but after examining the machine, you are not so sure. You begin asking yourself if you have done something wrong.