Typical wep app situation: you have logged in users querying for resources exposed through an API. As a hypothetical example, company administrators quering for their employees' time sheets:
company <- employees <- time_sheets company <- admin
Say I wanted to get all the time sheets that I'm authorized for/I have access to as an admin of that company.
Without any optimizations, in the above I'd have to join admin with company with employees with time_sheets to determine all the time_sheets I can look at. You can see how for a wider schema the joins could add up very fast. I realize that in modern databases joins are ludicrously fast, but I'm guessing this is still a case you don't want to completely ignore.
Is there a good solution to this? One could potentially have a separate admin to time_sheets many to many join table just to speed-up those queries, but then maintaining it might be tricky.