I'm trying to place a backend as close as possible to Vercel's iad1 deployment region, which appears to be associated with AWS us-east-1. Since us-east-1 has multiple Availability Zones, such as use1-az1 through use1-az6, is there any known advantage to choosing a particular one? I was considering use1-az1 by default, mainly to improve p99 latency and performance during high traffic, but reliability is also important. Any practical experience or guidance would be appreciated.
3 Answers
us-east-1 is probably the correct region, and the iad1 name refers to the Washington, D.C. area. However, the physical locations of the Availability Zones and Vercel’s infrastructure aren’t publicly mapped in a way that lets you choose the closest one. The AZ identifiers don’t reliably tell you which facility or network path will be nearest.
Northern Virginia has several large cloud facilities in the same general region, but there’s no guaranteed one-to-one relationship between an Availability Zone label and a particular building or route. If microsecond-level proximity is truly critical, a serverless deployment platform may not be the right architecture; otherwise, multi-AZ deployment and real p99 measurements will matter much more than guessing between use1-az1 and the other zones.
I wouldn’t optimize around a single AZ for reliability. Even if one happened to have slightly better latency, the difference may be tiny and the placement could change. A more resilient design would run the backend in at least two Availability Zones behind a load balancer, then measure latency and tail behavior from the actual Vercel deployment.
I’d use colocation if it were practical, so I was hoping choosing the same AZ might be the next-best option. I know the exact mapping isn’t public, but I’m trying to improve the reliability and p99 behavior of the parts of the setup I can control.