How can that be, you ask? All you have to do is take two slices of bread, spread some peanut butter on one slice, some jam on the other and slap them together, right?
That might be acceptable if you consume it immediately, but otherwise, no, you aren't doing it right. If you pack your lunch, you will very much regret your casual attitude towards PB&J.
I won't even go into the advanced math required to get the amount of filling right. Suffice it to say that you want as much filling as possible without any squirting out when you bite.
What I really want to talk about is the long term effects of jam on bread. It isn't pretty people.
jam + bread + time = goo.
Over the centuries there have been countless attempts to solve this problem, but most people don't even bother. This is wrong. But then most of the well known solutions aren't ideal. My grandmother used to spread room temperature butter on the jam side. This nicely solves the jam and bread problem, but unfortunately the result is no longer actually a PB&J sandwich, it is a PBB&J sandwich.
But there is a (nearly*) perfect solution. Spread a very very thin layer of creamy peanut butter on the jam side slice of bread before applying the jam. Really, this works great.
Why do I care how you make PB&J sandwiches? I don't. Not one bit. I don't even care if you agree with my solution. I am using PB&J as a metaphor.
But I'm not going to tell you what the metaphor is. That is an exercise for the reader.
I will, however, make the claim that if you read all of that and actually thought about whether that was a good solution to the problem, then you just might have the capacity to be a good software designer.
* - The solution is only nearly perfect because it slightly changes the slipperiness of the bread and the advanced filling calculations have to be redone.