In order to have global reach, you may be deploying your application in multiple geographical regions. When it comes to user request routing, you want to route their requests to the nearest and fastest available server for a quick response from your application. The DNS router provides the mapping between the domain names to the IP addresses and makes sure that the requests are served by the right server when the user types in the domain name—for example, when you type amazon.com in your browser to do some shopping, your request is always routed to the Amazon application server by the DNS service.

The public cloud-like AWS provides a DNS service called Amazon Route 53, where you can define a different kind of routing policy as per your application's need. Amazon Route 53 provides DNS services to simplify domain management and zone APEX support. The following are the most used routing policies:

• Simple routing policy: As the name suggests, this is the most straightforward routing policy and doesn't involve any complications. It is useful to route traffic to a single resource—for example, a web server that serves content for a particular website.
• Failover routing policy: This routing policy requires you to achieve high availability by configuring active–passive failover. If your application goes down in one region, then all the traffic can be routed to another region automatically.
• Geolocation routing policy: If the user belongs to a particular location then you can use a geolocation policy. A geolocation routing policy helps to route traffic to a specific region.
• Geoproximity routing policy: This is like a geolocation policy, but you have the option to shift traffic to other nearby locations when needed.

• Latency routing policy: If your application is running in multiple regions, you can use a latency policy to serve traffic from the region where the lowest latency can be achieved.
• Weighted routing policy: A weighted routing policy is used for A/B testing, where you want to send a certain amount of traffic to one region and increase this traffic as your trial proves more and more successful.

Additionally, Amazon Route 53 can detect anomalies in the source and volume of DNS queries and prioritize requests from users that are known to be reliable. It also protects your application from a DDoS attack. Once traffic passes through the DNS server, in most cases, the next stop will be a load balancer, which will distribute traffic among a cluster of servers. Let's learn about some more details regarding the load balancer.