How to increase performance in the View Port? I have model that has 100 000 cubes forming a 2d grid from a birds-eye view. The cubes are very simple in geometry, but still, with 100-200k it's hard to perform some tasks around the viewport.

Are there some options to remove and increase the performance? I've already disabled ambient occlusion, but it's still sometimes slow. Any advice?

NOTE: I don't want to cut the grid into multiple meshes and separate it in different layers if possible.
If your cubes have more than 8 verts then I suggest using a decimate modifier. But not applying it. It will reduce the polycount and you can just undo it for a final render by deleting the modifier.