MLO

An MLO is a custom interior: a police station, hospital, club, apartment or shop built as map data and streamed to clients. They are how a server gets spaces the base GTA V map does not provide, and they do more for a server's identity than almost any script.

They are also heavy. A detailed MLO carries geometry, collision, textures and sometimes its own props, and a server that installs twenty of them has materially increased every player's download and memory footprint. Placement conflicts are the other hazard — two MLOs claiming the same coordinates produce z-fighting, missing collision, or players falling through the world.

Performance-wise the thing to watch is LOD and occlusion: a well-built MLO hides what the player cannot see, a poorly built one renders the whole interior from outside the building.

For a new server, two or three excellent MLOs in places players actually spend time beat a map full of them.