"If you're worried about concurrency when incrementing a counter, you're at a level of scale few people get to work on."
I'm not sure I understand. If I make an application that has to increment a counter, shouldn't I always be worried about concurrency?
What I mean is, sure, if I'm serving only a few requests, then of course the probability of running into concurrency issues is lower than a site with more requests/sec. But it's still a matter of chance, there is some probability that two requests will come in at exactly the same time and cause a problem.
You are worrying about correctness of concurrency. Yes, this should always be worried about.
The parent poster is worrying about performance of concurrency. This doesn't need to be worried about unless you are one of about 5-10 tech companies whose name is recognisable to people on the street.
I'm not sure I understand. If I make an application that has to increment a counter, shouldn't I always be worried about concurrency?
What I mean is, sure, if I'm serving only a few requests, then of course the probability of running into concurrency issues is lower than a site with more requests/sec. But it's still a matter of chance, there is some probability that two requests will come in at exactly the same time and cause a problem.