> I don't think there is a distance limit between AZs but instead a latency limit

Ok, fleshing that out via google:

"The connection between AZs is expected to typically achieve low single-digit millisecond latency between them on average."

https://knowledgebase.progress.com/articles/Article/expected...

and

1 light-millisecond = 299792.458 meters, so nearly 300 km / 186 miles.

https://www.translatorscafe.com/unit-converter/en-US/length/...

So in 2 milliseconds, light travels 599km or 372 miles.

That's a _hard_ limit. IIRC, modern communications is at a fraction of lightspeed, which would lower it.

There's no reason _not_ to have the AZs for a region in the same metro area, so separated by 10s of km, tops.

10km = 0.0333 light-milliseconds.