“With ~63k entries that’s (n^2+n)/2 = (63000^2+63000)/2 = 1984531500 checks if my math is right.”
GTA Online took six minutes to load for seven years. The cause was a 10MB JSON file parsed with sscanf, which calls strlen on the whole buffer every time, plus a duplicate check over a list that had no duplicates. One player found it with a decade-old profiler and no source code. Rockstar paid him $10,000 and shipped a fix two weeks later. That game made billions while nobody inside looked.