Amazon Route 53's ALIAS implementation takes a different approach. We only allow ALIASes to data that we know about authoritatively; so with Route 53 you can ALIAS to an S3 website Bucket (which also lets you do HTTP redirects), a CloudFront distribution (which can serve as a bridge to any arbitrary domain you may care), an ELB or to other records in your zone (which lets you combine routing policies in a compositional way).<p>The main benefits are;<p><pre><code> No dependency on a third party DNS service, we stand behind our 100% SLA
DNS-based routing policies still work correctly
No delay in responding to health check failures
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but there's another (future, for us) ancillary benefit too;<p><pre><code> Compatibility with offline-signed DNSSEC
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The big downside of course is that the record has to be in our system in order to ALIAS to it. For HTTP services, using CloudFront is a pretty good workaround, it can handle dynamic and static sites. If you merely want to redirect from your apex to your www. domain, then S3 with a redirect works great too.<p>We're also open to enabling ALIASing to other zones hosted in Route 53 on a case by case basis. If you have a multi-tenant service and you're managing (or willing to manage) a zone on Route 53 with something like [customer-or-resource-identifier].yourservicename.com we can enable ALIASing to those names. If you're interested, get in touch via the limit increase process; <a href="http://docs.aws.amazon.com/general/latest/gr/aws_service_limits.html" rel="nofollow">http://docs.aws.amazon.com/general/latest/gr/aws_service_lim...</a> .<p>Obvious question: Why don't we enable ALIASing across zones by default? Firstly, zones which can be aliased to have to be replicated and available in all shards of our partitioned datastore (some day we may use some kind of cross-shard query protocol to resolve that, but even then we'd prefer to minimize the traffic) and secondly we want to ensure some stability for ALIAS targets and avoid situations where targets may be discontinued or deleted by their owners leaving our mutual customers stranded.