Are read-only transactions handled without contention? I understand that a read-write transaction needs to be aborted if a later conflicting write is committed. But read-only transactions can view a snapshot of what was committed before they begin - you trade a little bit of latency for being conflict free. It doesn't even have to be the default as long as you offer it as an option, you might want this if you know you are reading hot keys, or as a fallback if you've been aborted X times.

This was IMO the big innovation of true time in spanner - contention free reads at either now, or at some time in the past.