(i work at aws) yes, while in my opinion most services won't care about the distinction between cross-az/same-az (you're definitely not most services :) ), you

(i work at aws) yes, while in my opinion most services won't care about the distinction between cross-az/same-az (you're definitely not most services :) ), you can definitely tell the difference between * in the same region vs not * in the same az vs not * in the same placement group or not which shouldn't be surprising. you should get a latency benefit from increased physical proximity!