Scenario: You have a transformation which loses information. For example you grab the birth date and you store the age of the subject. Then the data becomes old and useless.

Problem: It is impossible to easily fix the data.

Solution: Dump the age of the subject and store its birth date. Then the age can be calculated on the fly.

Whenever somebody improves the performance too much, it is losing some precious information, which makes some operations incredible expensive if not downright impossible.

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See also DontLoseGoodIdeas

See PrematureOptimization.