Like if you want to increase the game speed when you have tons of zombies then turn off their collision to other entities (blocks is fine’ish), and batch their pathfinding together when they are near, lol.
Just remember, every entity in a chunk checks to every other entity in the chunk, exponential, lol.
Though if you want to look at costly, you should see what the engine does once it finds that there is a collision, now that’s bad!