Multi AZ is actually fairly easy to do, only difficulty is in some special cases. Multi region is a bit harder due to higher latency. IMO you should do everyth

Multi AZ is actually fairly easy to do, only difficulty is in some special cases. Multi region is a bit harder due to higher latency. IMO you should do everything you can as multi AZ and if there are some services that are harder to do and you don't need it, then put them in a single AZ. Thing is that if you keep everything in a single AZ it will be much harder to change when this requirement become important.