When knowledge is the limiting factor
In Why Information Grows (my review), physicist César Hidalgo explains that the difference between the ability to produce tee shirts vs rockets is a matter of accumulating knowledge and know-how inside people, and weaving those people into networks. Because no one person can know how to build a rocket from rocks. No one person understands how a laptop computer works, at all levels. There’s a limit to the amount of knowledge a single person can cram into their head in a lifetime; Hidalgo calls this limit one personbyte.
Our software systems are more complicated than one person can hold. You can deal with this by making each system smaller (hello microservices), but then someone has to understand how they fit together. And someone cannot. It takes teams of people.
You can deal with the personbyte limitation by forming teams that work together closely. The more complex the product we’re building, the more knowledge we need, so the less duplicated knowledge we want on the team. Team size is limited too, because of coordination overhead.
If you think about it this way, you might recognize that in many software teams, our limitation is not how much we can do, but how much we can know. To change a sufficiently complex system, we need more knowledge than one or two people can hold. Otherwise we are very slow, or we mess it up and the unintended effects of our change create a ton more work.
If the limitation of my team is how much we can know, then mob programming makes a ton of sense. In mob programming, the whole team applies their knowledge to the problem, and each person takes turns typing. This way we’re going to do the single most important thing in the most efficient and least dangerous way our collective knowledge and know-how can provide. In the meantime we spread knowledge among the team, making everyone more effective.
If your software system has reached the point where changing it is one step forward, two steps back — it might be a good time to try working as one unit, mob-programming style.