Imagine you have an employee database and a table for each employee which contains their start date. There are other tables which describe their vacation allowances based on role, seniority and month of hire. There is also a table which contains the vacation used for each employee.
From a general, balanced perspective of performance and ease of code and maintenance, is it better to compute an employee's vacation balance by evaluating all the table data or to store the available vacation in buckets which are then adjusted as vacation is taken.
It seems to me the overhead and complexity of calculating the available vacation, then computing the vacation which has been taken is unnecessary and a more efficient and graceful solution would be to create a table which holds the available vacation, populate it at the beginning of the year and decrement it as vacation is taken.