The worst case (satellite as near the horizon as possible, so as far away from you as possible) speed of light lag for a signal to reach the sat is <3ms. Since

The worst case (satellite as near the horizon as possible, so as far away from you as possible) speed of light lag for a signal to reach the sat is <3ms. Since a request-response cycle needs to hop 4 times (req up, req down, resp up, resp down) the worst case lag over a single satellite hop is <12ms. If the other endpoint is not within the field of view of the same sat as you, there needs to be a second hop, from the ground station up to the sat and back down again, which adds another up to 12ms, and so on and so on. Alternatively, they will likely put a ground station on top of all IXPs and from there the signal goes on fiber.