Your staging site is lying to you

Staging environments earn their keep on structure and break their promise on scale. A hundred rows instead of two hundred thousand. No concurrency. A machine with different limits, and half the caching layer switched off so developers can see their changes.

That is fine, as long as nobody says “it worked on staging” like it settles the question. It settles whether the code runs. It says nothing about whether it runs under load.

The cheap fix: keep one environment with production-shaped data, anonymised and full size, and run anything performance-sensitive there before it ships.