We have a concept of the Particle Horizon, the max distance light could have traveled in the universe, and that is our boundary, our effective edge of the universe.

There's the concept of the light cone, which is the total volume of observable light which can ever reach an observer, or inversely, the total volume ever traveled by a given point source. The expansion of the universe means that there is a certain boundary, a horizon where the universe expands too much for light to ever travel the required distance.

https://en.m.wikipedia.org/wiki/Particle_horizon

https://en.wikipedia.org/wiki/Light_cone