‫Okay, so we've seen the global services,
‫but how do we have a global application?
‫Well, let's discuss architecture a little bit.
‫So if we have a single region, single AZ, it's very simple.
‫We have an EC2 instance in one easy in one region
‫that does not give us high availability, for sure.
‫This does not give us good global agency,
‫because if we access this institution
‫from a user that's very, very far away
‫from a region is going to get bad at latency.
‫And it's very, very simple to set up.
‫So very, very low difficulty.
‫Next, we have a single region, multi AZ.
‫So here we have two AZs within one region.
‫So we do have high availability,
‫but we do not have improvements for a global agency.
‫So again, the AZs are close to each other.
‫And so if we take a point in the well
‫that's far away from my AZs
‫then we're going to have high latency.
‫And the difficulty is a little bit increased,
‫but not that much.
‫Next we have a multi-region called active passive.
‫And remember that term so active passive,
‫it means that we have two regions.
‫Each region has one or multiple AZ
‫and in one region our EC2 instances are going to be active,
‫or our application is going to be active.
‫That means that our users,
‫wherever they are in the world can do reads
‫and writes to our EC2 instance in the active region.
‫And the other one EC2 is passive.
‫That means that there is data replication
‫between the active region and the passive region.
‫And possibly the users can do reads from the passive region,
‫but they can not do writes to the passive region.
‫That's why it's called passive, active passive.
‫And so with active passive,
‫well, if we have many regions around the world
‫and they're all passive, that means
‫that we are going to have improved read latency
‫because now we have our data replicated
‫across the world and with low latency,
‫but for writes well, all the writes still need to go
‫to the same central region.
‫So that means that the writes at a global level
‫still have the high latency.
‫And finally, well, it's definitely increased difficulty
‫because now we have multiple regions,
‫so that's active passive,
‫and finally we have active active.
‫And so this is where each EC2 instance
‫is able to take writes and reads,
‫and there is replication still happening
‫within these two instances.
‫So this improves the read latency,
‫the write latency at a global level, obviously.
‫And it's higher difficulty because now your application
‫has to do a lot of things in every single region
‫and is more difficult to set up.
‫But for example, a database
‫that is having an active active demo setup
‫is dynamoDB global tables as we've seen before.
‫Okay, so if you remember just what these means,
‫active active, active passive, multi-region, single region,
‫you should be good to go for the exam
‫to answer one question.
‫All right, that's it.
‫I will see you in the next lecture.