The speed of light is the only condition or space/time ratio that would make an entity at that speed experience zero proper time (a sort of instantaneousness, teleportation or entanglement in spacetime, no matter what interval is involved for other observers).

So every physical process we observe is also an instant action/reaction event for the massless quanta and field disturbances involved.

If you are interested in the implications that this "speed of light = instantaneousness" duality has in solving all quantum and cosmological riddles, check out my Medium profile: https://quantumwormholes.medium.com

I also recommend reading "Understanding Our Unseen Reality" by Ruth E. Kastner (2015) and "Helgoland" by Carlo Rovelli (2021), two easy and informative books about the Transactional and Relational interpretations of Quantum Mechanics, fully compatible with this new way of understanding interactions and how energy or information exchanges unfold in the universe.