Do you just ask them to walk you through the architecture by memory? If so what how do you come up with questions about their choices without the specificities of the actual way they wrote their code?
Basically see if they could communicate how the system worked, it’s good points and bad points, and how deep they could go. This quickly separates the good developers from the cargo culters and pretenders. It also is a good gauge of how much real experience they have had.
Generally, if someone can’t describe at least the rough outline of the architecture of an application they have worked on, that’s a strong signal they are going to struggle as a developer
depends on the role, e.g. for infra work i can ask "if you had complete autonomy to stand up this project again, what would be your first step" and then we go from there