Why does CodeChef take so long to update their rank list after any contest?

I have taken part in many coding contests across many websites but a question that was actually lingering in my mind was that Why does CodeChef take so long to update their rank list after any contest?be it the long contest or any short contest while many other sites like codeforces,hackerrank updates their rating just after 1-2 hours of the contest.The no of participants are also very high in codeforces div-2 contest as compared to the short contest of codechef. codeforces,hackerrank ,hackerearth too checks for plagiarism the way codechef does.
@admin then what is the reason for the delay in the updation of ratings.

This is because Codechef often runs moss test on solutions to detect plagiarism!

but it is run by other sites as well which update their ranks within hours

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