The success of the project as a whole is measured, of course.
But it's 20 people working on it, from design to sales to ops to customers relations to devs. How could you possibly pin 20% of the profit (not even the turnover, but the profit) on one guy?
Even if he improved the SQL queries and that immediately led to more sales, making the choice to work on that over other things was probably not his.
Nobody is asking to pin all that on exactly one person. That’s a silly overly engineery way of looking at it.
It’s a team effort. Being part of the team who did X is enough. You can then talk about your specific individual contribution when appropriate.
Just like everyone in an NBA team “wins the championship” and gets to put “winner” on their resume. Or how hockey players say “I won the Stanley cup”, even though they did it as a team.
This seems to be completely counter to your initial post tying weekly/daily work directly to profit to determine what is worth your effort and what to put on your resume. You even give SQL queries as an example, so I don't see how that's not trying to tie it down to the lines of code.
There's a big difference between:
1. I optimized SQL queries for Nameless Corp to increase profits 20%
2. I optimized SQL queries for Nameless Corp on a multi-million dollar project.
But it's 20 people working on it, from design to sales to ops to customers relations to devs. How could you possibly pin 20% of the profit (not even the turnover, but the profit) on one guy?
Even if he improved the SQL queries and that immediately led to more sales, making the choice to work on that over other things was probably not his.