The easiest way to have a counter that is both correct and fast is to split things up into multiple separate counters and then count them. So for a simple example: User ID mod 50 = 7 so lock row, 7 increment row, 7 unlock row 7. Want the total? sum (all rows).
You can also get fancy with lock row 1, lock total, update total = total + value of row 1, unlock total, set row 1 to 0, unlock row 1. Repeat row 2...50. The advantage being even lower latency access to a number that is withing X seconds of being correct.
PS: Both of the above can be split across multiple cores / machines. But, for a less accurate but still reasonable have the client a = (rand (0,100)), b = rand (0, 100 + a), if b == 7 update death count by (a + 100). This only increments the counter 1 time in ~150 times while avoiding counters that are always multiples of some number. Just be careful of off by one errors.
You can also get fancy with lock row 1, lock total, update total = total + value of row 1, unlock total, set row 1 to 0, unlock row 1. Repeat row 2...50. The advantage being even lower latency access to a number that is withing X seconds of being correct.
PS: Both of the above can be split across multiple cores / machines. But, for a less accurate but still reasonable have the client a = (rand (0,100)), b = rand (0, 100 + a), if b == 7 update death count by (a + 100). This only increments the counter 1 time in ~150 times while avoiding counters that are always multiples of some number. Just be careful of off by one errors.