I hope this is on-topic. It's not directly about personal finance, but it's not an academic economics question either. It is about what happens behind the scenes.
The question is motivated by the recent brief negative price of short-term oil futures. I understand why it happened - storage became so hard to find that people didn't want to take possession of the oil. But I am curious about the moment where the first person realized that they were going to have to pay someone to take the contract. Are all trades settled electronically, so that someone just had to swallow hard and enter a negative number in the asking price box on a screen? Or would phone calls have been made?
Whenever I try to research this online, I get an investor's perspective rather than a trader's perspective, because there are far more investors than traders, and there are far, far more amateur or beginning investors than there are traders who need this explained. But I would like to understand what that inversion would have looked like from a trader's perspective, that is, from the point of view of the person (if there is still such a person) who actually matches the buyer up with the seller.