How Cloud Deploys our Application Across the Globe? – Part 1


Cloud providers deploy our service across the globe in different regions and availability zones to keep the service available, have a contingency plan for disasters and place the code near the end-user to cut down network latency.

A region is a geographic area. For instance, Las Vegas, Delhi, Melbourne, and Toronto are different regions. A region contains multiple availability zones, also called AZs. Further, these AZs contain multiple data centers. Regions may also contain multiple local zones or LZs.

Illustration 1.33 - Regions, AZs & Data Centers

Taking AWS Global Infrastructure as a reference, its Ohio region contains three availability zones. The Tokyo region contains four availability zones. The Oregon region contains four availability zones, one local zone, and so on.

Local zones are an extension of a region in case additional computational power or other infrastructural resources are required in a region. LZs can be set up near the end-user to augment the regions’ power and cut down the latency.

A local zone set up near the end-user helps deploy latency-sensitive services like stock trading, online multiplayer games, and so on.

If we have deployed our service in a region and want to cut network latency down, we can take advantage of local zones. However, not all regions have the ability to set up local zones. The availability of an LZ in a region largely depends on the cloud provider.

Communication between regions, availability zones, and data centers

Regions are kept physically isolated and independent of each other in terms of power supply, water supply, hardware, etc. This ensures service availability and fault tolerance from a regional perspective. If any region goes down, it doesn’t impact the other regions.

Also, there are often legal constraints on companies dealing with sensitive data to keep it within a certain region. Having isolated deployments in different regions enables them to comply with the law. The government and other legal entities do not want their data to be replicated to other regions across the globe for obvious security reasons.

The availability zones contain multiple data centers. Every respective availability zone is run by its own set of data centers. Data centers are not shared between the availability zones to ensure service availability and fault-tolerance at the zonal level. If an AZ goes down due to a local disaster, the other availability zones are not impacted.

An availability zone is generally run by two to three data centers. A large availability can also be run by five to six data centers.

Within an availability zone, the data centers are connected to each other via a low latency network. Even the network is made redundant to cope with any sort of failure. When we deploy our application on the cloud, we are prompted by the cloud provider to select a region and an availability zone to run our application in.

Ideally, the region and the AZ nearest to our end users are selected to keep the network latency low.

The cloud deploys our application spanning multiple availability zones to avoid a single point of failure from an AZ standpoint. Even if an entire zone goes offline, the requests will be routed to a different zone. This is achieved with the help of a load balancer that runs at a regional level outside the zones. These load balancers have a regional scope.

This is the standard setup of regions, availability zones, and data centers. Businesses can always tweak their deployments based on their requirements with the help of cloud providers.

Illustration 1.34 - Service Deployed On The Cloud Across Multiple AZs

This is a good read on how AWS ensures service availability during natural or man-made disasters.

Here is a nice visual tool that gives insight into Google Cloud’s global infrastructure.

Recommended read: A closer look at Netflix’s Christmas Eve Outage.

In the next lesson, let’s discuss multi-regional deployments.

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