#concurrency

A celebrity posts and a million people tap the heart in ten minutes, and every one of them sees a count that seems to keep up. One row with a number in it can't take that. So what does?

Two requests read the same row, both do their maths, both write back. One of them silently disappears. How the system should resolve that isn't one answer: it depends on whether the write is a delta, a quick piece of logic, or a human edit made minutes after the read.