First of all, I should say that I think that this question does not belong on Meta.
StackOverflow URLs are inspirational to me, the way they are designed is very clever and they work really well but I can't seem to understand the logic being the IDs, here are some examples:
If you change the ID to ID++ (
2121721) one could think it would fetch the next question. Wrong, instead you're redirect to another question whose ID seems to be totally unrelated (
Why does this happen? Is there some checksum algorithm on the IDs? Here is a sample trace:
2121720 -> exists 2121721 -> 2121212 2121213 -> exists 2121214 -> 2121155 2121156 -> exists 2121157 -> 2120884 2120885 -> exists 2120886 -> 2115014 2115015 -> 2114896 (what happened here?) 2114897 -> 2114799 2114800 -> 2114670 (what happened here?) 2114671 -> exists 2114672 -> 2110215 2110216 -> exists 2110217 -> 2106982 2106983 -> 2106955 (what happened here?)
The IDs seem to decrease. Can someone bring some light on this strange redirect behavior?