Does Unreal prevent mesh rendering behind a wall?

A question: If my FPS character is in a room without windows, will the engine render the things outside the wall?

Example: A house with a yard. There’s no windows on a particular wall, so the meshes outside should not be rendered.

Because I’m having some performance issues with my game, although my draw calls number and texture streaming are not high.

Yes, it does do occlusion culling. You can visualise what is and isn’t culled by using the console command r.VisualizeOccludedPrimitives.

There are all kinds of reasons why you might be getting poor performance, from intensive blueprint logic to excessive overdraw. Here are Epic’s performance guidelines for building content for the engine.

You also have to make sure that things are split up in such a way that it can hide parts that aren’t visible. So for example the exterior would be made from separate meshes.