I startet at this company where they made a map where some locations where displayed on a map. It took like 30 seconds to load the locations - and it could only display ten at once. To cover this fact they made it impossable to zoom out...
I circumenvented their incredably bad orm and queried the DB directly, created some indices, and only shipped coordinates, type and label (whereas they shipped the whole datasets to the browser before) - and suddenly i could show all 30k
pins at once in microseconds having less traffic then before. That was quite a leap.

Needless to say the app never reached nearly production, I left the shit show soon after and the ceo is dead by now.