ELB vs Route 53 routing
ELB duty is to distribute traffic to instances while making sure that the instances are healthy to make sure your application is always available.
Route 53 has many functionality which are called polices and they are;
**simple, weighted, latency, failover and geolocation. **
Unlike ELB, with Route 53 weighted policy you can manually set the traffic distribution for your applications like 20% traffic should be routed to instance A while 80% should be routed to instance B.
In the case of failover, both Route 53 and ELB do have similar functionality by routing traffic to only health application or instances. But for Route 53, you use fail-over for active passive fail-over.
Latency with Route 53 respond to DNS queries with the resources that provide the best latency. This means that Route 53 chooses to respond to the DNS query based on which data center gives your user the lowest latency.
Geolocation is when you want Amazon Route 53 to respond to DNS queries based on the location of your users. But Geo-location do have a functionality of presenting the user the ability to change the content like languages to suit the users.
Simple is just plain simple : )
Now lets discuss about the differences between them ..
ELBs are intended to load balance across EC2 instances in a ‘single’ region. Whereas DNS load-balancing (Route 53) is intended to help balance traffic ‘across’ regions. Route53 policies like geolocation may help direct traffic to preferred regions, then ELBs route between instances within one region.
Functionally, another difference is that DNS-based routing (e.g. Route 53) only changes the address that your clients’ requests resolve to. On the other hand, an ELB actually reroutes traffic.
One analogy is: if you ask for the closest WalMart, you may get an address based on your location, but you could choose to go to another Walmart if you know one. That’s Route 53; it just switches the address resolved based on some context. On the other hand, a policeman redirecting traffic because of construction, is more like an ELB, he/she is actually changing the traffic flow, not just suggesting.
There are additional considerations about whether DNS-based routing versus Load Balancing is best for your use case, and why (or if) Route53 and ELB continue to co-exist, but hopefully this helps at a high-level.
Another difference is with ELB you can use autoscaling to automatically register new instances added to the group with the ELB, you do not have to do anything yourself. With Route53 you have to either manually replace the old failed instance with the new one in the route or add some script to your launch configuration to automatically register the new instance with Route53 and remove the failed one.
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Happy learning!
