Quick answer: Pygame tilemap rendering slow after switching to scaled tiles? pygame.transform.scale runs per-blit; pre-scale once at load time.
Original 16x16 tiles; player wants 32x32. Per-frame scale costs 8ms; pre-scaled costs 0.5ms.
Pre-scale at load
Load tiles; scale once via pygame.transform.scale_by; cache the result. Per-frame blit is fast.
Or use SDL2 GPU scale
Through pygame's GPU surface; let the GPU scale. Free for the CPU.
Avoid mid-frame transform
Any transform per-frame is a candidate for caching.
“Per-frame transforms are CPU work. Caching is the universal cure.”
Audit your render loop for transform calls. Each is a candidate for pre-computation.