Mesh clipping/collision events?

I’m working on a project that places meshes in various places of a given area, and I was wondering if there is an efficient way to check if two separate meshes are in the same coordinate.

The system itself works off of a basic integer X and Y system (it is then multiplied by some value to give it an actual coordinate), and I figure that I can simply add every instance into an array and compare values before placement. however, as you can imagine, this would be extremely expensive memory wise when the number of instances reaches hundreds and hundreds. Although it may only need to occur once, I would prefer to find a more efficient way. Do you guys have any suggestions?