‫The first service
‫that is going to be very important for
‫us to deploy a global application is Amazon Route 53.
‫So, Route 53 is a managed DNS or Domain Name System.
‫And what does the DNS?
‫Well, DNS is just like a phone book.
‫It's a collection of rules and records,
‫which help clients find the right servers through URLs.
‫So let's go through the most common records in AWS.
‫For example,
‫say you are mapping www.google.com to an IPv4 address.
‫Then this is called an A record.
‫If you are mapping www.google.com to a long IPv6 address,
‫it's called the quadruple A record.
‫Also, if you map a host name to another host name,
‫so search the www.google.com come into the previous address.
‫It's called a CNAME because we're
‫mapping a host name to host name.
‫And then finally,
‫if you're mapping a host name into an AWS resource,
‫it's a special type of record called an Alias record.
‫And that works for you if you have an ELB,
‫or if using CloudFronts, S3,
‫an RDS database, et cetera, et cetera.
‫Now, going into the exam,
‫you don't need to know all the types of records,
‫but I just wanted to give you an overview of
‫them in this lecture.
‫So, from an Exam perspective,
‫Route 53 is a managed DNS,
‫but let's go one step further because you need to
‫understand a little bit better how it works.
‫So for example,
‫for Route 53 say,
‫we want to see what happens for an A Record.
‫So our Web browser is here.
‫That's a Web browser,
‫and we have an Application Server that we've deployed that
‫has a public IPv4.
‫Now we want to be able to access our application server
‫using a normal URL.
‫So for this, we're going to go into Route 53 and
‫we're going to create a, A Record.
‫And so that when the Web browser does
‫a DNS Request for myapp.mydomain.com
‫then the DNS will reply back with an IP.
‫And then that IP can be used by our Web browser to
‫get to our correct server.
‫and then get the HTTP Response from our server.
‫And this is the basics of how a DNS work at
‫a very, very high level.
‫What you need to understand as well for Route 53,
‫from an Exam perspective is the Routing Policies.
‫So, we need to know them at a high-level and decide what's
‫the right one based on the use case,
‫because you'll see, it's pretty simple.
‫So, the first one is called a Simple Routing Policy,
‫which has No health checks.
‫So our Web browser will go into our DNS system,
‫does a DNS query and gets an IPv4 for example as a result,
‫that's a Simple Routing Policy.
‫The basic one, we can understand.
‫The Weighted Routing Policy,
‫allows us to distribute the traffic across
‫multiple Institute instances.
‫So in this example,
‫we have to assign weights to our Institute instances,
‫for example, 70, 20, and 10,
‫and then our DNS we'll make sure that our clients have
‫70% of the traffic onto the first one,
‫20% of the traffic onto the second one and
‫10% of the traffic on to the third one.
‫This is effectively some kind of load balancing.
‫So in this Weighted Routing Policy,
‫we can use health checks.
‫Next, we have the Latency Routing Policy.
‫So in this example,
‫we'll say we are displaying our application globally,
‫one in California,
‫and the other one in Australia.
‫And our users are all around the world.
‫The Latency Routing Policy we'll look at where
‫the user is located.
‫And if they're located close to
‫our Kelly American Institute instance,
‫then they will be redirected to talk to that server.
‫And if they're close to Australia,
‫then they will be redirected to
‫talk to the Australia server.
‫And this is based on the latency.
‫So, in this example,
‫Route 53 will be used to minimize the latency between the
‫users and the servers by making the
‫users connect to the server.
‫That is the closest to them.
‫And then finally,
‫we have a Failover Routing Policy in which
‫we have a client and we have
‫a primary institute instance and a Failover one.
‫And so our DNS system will do a Health check On the primary.
‫And in case the primary instance fails,
‫then we will be redirected to the failovers.
‫This helps with disaster recovery.
‫So the clients will know exactly thanks to Route 53,
‫which instance to connect to based on the
‫health of that instance.
‫So that's it,
‫that's our the four Routing Policies you need to know.
‫Just a first one does not have a Health check.
‫All the other ones have Health checks and they
‫all serve different purposes.
‫So, Weighted Routing Policy is to distribute the
‫traffic across multiple institute instances.
‫Latency is to minimize latency and
‫Failover is to help with Disaster Recovery.
‫So hope that was helpful.
‫And I will see you in the next lecture.