Comment by alphazard
> wouldn't be a bug if everything was happening exactly according to expectations
This isn't quite true, especially concerning distributed systems. It's relatively common for a software system to be broken by design. It's not that the developer didn't know how to use the programming language to get the computer to do what they want. It's that what the developer wanted reflects a poor model of the world, a logical inconsistency, or just a behavior which is confusing to users.
Keep in mind I said that this is advice I give junior engineers specifically; they shouldn't be the ones responsible for designing distributed systems in the first place. For someone in that part of their career, this advice is meant to help to learn the skills the need to solve the problems they're dealing with, and it's not intended to be universal to all circumstances, just a useful thing to keep i mind.