[Johnny555]

I've heard the reason is because that's where they roll out maintenance first

That doesn't make sense - why would they do maintenance in their largest (and oldest) region first? I'd expect them to roll out changes to smaller regions first so problems will affect fewer users.

I think the more likely explanation is that it's their largest (and oldest) region.

[swasheck]

an aws tam once told me the same thing. us-east-1a gets the new stuff first. i never validated it against anything other than this one person's statement.

[ecnahc515]

"1a" in this context means nothing. The AZ assignments each account gets is random. us-east-1a is probably a different data center for you than me.