>>A project where C programmers spend five hours to make it run in 4 seconds is in this caveat "20% faster" than a project where Alt Lang programmers spend five minutes to make it run in 5 seconds - because only those seconds count. This is not how the real world works so it's a pretty nasty caveat.
For any project with non-trivial amount of users the C programmer did better.
I mean I know companies like to save money and move the costs (time, electricity, hardware costs) to customers but if you care about users any non-trivial speed improvement is worth a lot in aggregate, surely more than your time implementing it.
Databases are a problem space which can absorb all available effort. So if you spend five hours making thing U as fast as it could be that's five fewer hours you can dedicate to thing V or thing W, not to mention X, Y, Z and so on.
For any project with non-trivial amount of users the C programmer did better. I mean I know companies like to save money and move the costs (time, electricity, hardware costs) to customers but if you care about users any non-trivial speed improvement is worth a lot in aggregate, surely more than your time implementing it.