>Services like DynamoDB maintain hundreds of thousands of DNS records to operate a very large heterogeneous fleet of load balancers in each Region
Does that mean a DNS query for dynamodb.us-east-1.amazonaws.com can resolve to one of a hundred thousand IP address?
That's insane!
And also well beyond the limits of route53.
I'm wondering if they're constantly updating route53 with a smaller subset of records and using a low ttl to somewhat work around this.
DNS-based CDNs are also effectively this: collect metrics from a datastore regarding system usage metrics, packet loss, latency etc and compute a table of viewer networks and preferred PoPs.
Unfortunately hard documentation is difficult to provide but that’s how a CDN worked at a place I used to work for, there’s also another CDN[1] which talks about the same thing in fancier terms.
[1] https://bunny.net/network/smartedge/
Akamai talked about it in the early 2000s. Facebook content folks had a decent paper describing the latency collection and realtime routing around 2011ish, something like “pinpoint” I want to say. Though as you say was industry practice before then.
Some details, but yeah that's basically how all AWS DNS works. I think youre missing how labels, zones, and domains are related but distinct. And that R53 operates in resource record SETS. And there are affordances in the set relationships to build trees and logic for selecting an appropriate set (eg healthcheck, latency).
> And also well beyond the limits of route53
Ipso facto, R53 can do this just fine. Where do you think all of your public EC2, ELB, RDS, API Gateway, etc etc records are managed and served?
I haven't tested with dynamodb, but I once ran a loop of doing DNS lookups for s3, and I in a couple seconds I got hundreds of distinct ip addresses. And that was just for a single region, from a single source ip.
> And also well beyond the limits of route53.
One thing is the internal limit, another thing is the customer-facing limit.
Some hard limits are softer than they appear.