AWS Region vs Availability Zone: What is the Difference?

Every newly deployed software product aims to scale. Companies dream of seeing people use their products, whether that’s the growing the number of users from one country or promoting new user interactions around the world. When that growth happens, the question is: Can the product deliver a positive experience – fast results, low latency – to every user?

In the past, achieving global scalability without sacrificing user experience was complex and expensive. Having data centers physically located far away from users results in long page loading times and high latency.

Today, with cloud computing providers like AWS and their multi-region application architecture, you can easily distribute your application worldwide to serve your customers and be fault-tolerant. Over 90% of Fortune 100 companies leverage the AWS Partner Network (APN) to develop services and solutions for their customers.

What is an AWS Region?

An AWS Region is a physical cluster of data centers located in a specific geographic area. Each Region is independent and designed to be completely isolated from other Regions. If there is a problem in one Region, it is unlikely to affect other Regions. This level of isolation is critical for workloads with compliance and data sovereignty requirements, where you must guarantee that user data does not leave a specific geographic region.

Not all AWS services are available in every region. For example, the Amazon SES (Simple Email Service) is not available in the Europe (Zurich) region. While many AWS users wish to keep their data in a particular region for data sovereignty purposes, Amazon SES is used to send emails to the internet, so it does not really need to fit this data governance model – you’ll send the email outside of the region anyway.

If the service you want is unavailable in a particular region, you can still use the service in another one.

List of AWS Regions

There are 32 AWS Regions in operation worldwide as of October 2023, with announced plans for four more. They are located:

7 in North America

8 in Europe

3 in the Middle East

10 in Asia Pacific

2 in Australia and New Zealand

1 in South America

1 in Africa

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Each AWS Region is identified by an API (code) name that gives its rough location. For example, North Virginia has the code us-east-1 as it’s the first designated region in the eastern United States. The other is Ohio, with its code us-east-2.

Below is a list of available AWS Regions as of October 2023, with their codes.

Region Name | Code
Africa (Cape Town) | af-south-1
Asia Pacific (Hong Kong) | ap-east-1
Asia Pacific (Tokyo) | ap-northeast-1
Asia Pacific (Seoul) | ap-northeast-2
Asia Pacific (Osaka) | ap-northeast-3
Asia Pacific (Mumbai) | ap-south-1
Asia Pacific (Hyderabad) | ap-south-2
Asia Pacific (Singapore) | ap-southeast-1
Asia Pacific (Sydney) | ap-southeast-2
Asia Pacific (Jakarta) | ap-southeast-3
Asia Pacific (Melbourne) | ap-southeast-4
Canada (Central) | ca-central-1
China (Beijing) | cn-north-1
China (Ningxia) | cn-northwest-1
Europe (Frankfurt) | eu-central-1
Europe (Zurich) | eu-central-2
Europe (Stockholm) | eu-north-1
Europe (Milan) | eu-south-1
Europe (Spain) | eu-south-2
Europe (Ireland) | eu-west-1
Europe (London) | eu-west-2
Europe (Paris) | eu-west-3
Middle East (UAE) | me-central-1
Middle East (Bahrain) | me-south-1
Israel (Tel Aviv) Region | il-central-1
South America (Sao Paulo) | sa-east-1
US East (N. Virginia) | us-east-1
US East (Ohio) | us-east-2
AWS GovCloud (US-East) | us-gov-east-1
AWS GovCloud (US-West) | us-gov-west-1
US West (N. California) | us-west-1
US West (Oregon) | us-west-2

Out of the above 32 available regions, US East (N. Virginia), US West (Oregon), Asia Pacific (Singapore), Asia Pacific (Sydney), Asia Pacific (Tokyo), Europe (Frankfurt), and Europe (Ireland) are the regions with the most services available.

How to choose an AWS Region

Choosing the right AWS Region is a crucial decision that can significantly impact your applications’ performance, latency, and regulatory compliance. Consider the following factors when selecting an AWS Region:

Proximity to users: Choose a region closest to the majority of your users to reduce latency and improve overall performance. If you have a large-scale application that has multiple users across the globe, deploying in several regions might be better so you can still deliver the best experience to everyone.

Compliance and data residency: Ensure the selected region complies with the data residency and sovereignty requirements specific to your industry and user base.

Service availability: Verify if the AWS services you intend to use are available in the region you are considering.

Cost: Evaluate the pricing differences across regions, including data transfer costs, storage fees, and other service-specific charges as they can vary based on the region. Amazon provides a handy AWS Pricing Calculator that estimates each AWS Region’s cost based on your requirements.

SLA varies by region: Just as with cost, your SLA details will vary by region, so be aware of your needs and if they’re being met.

What are AWS Availability Zones?

An AWS Region consists of multiple Availability Zones. AWS Availability Zones (AZ) are isolated locations within an AWS Region designed to be independent and resilient from failures in other AZs.

Each Availability Zone is equipped with its own power source and network connectivity and is housed in its own facility. All of them are interconnected with high-speed and low-latency, with the use of a shared responsibility model to allow reliable, synchronous data replication and redundancy. This architecture ensures that applications can continue running seamlessly from another zone within the same region if one Availability Zone goes offline.

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List of AWS Availability Zones

Currently, 102 AWS Availability Zones operate worldwide, averaging about three per AWS Region. AWS announced plans for twelve more AZs across the four new regions yet to be activated.

Each Availability Zone also has a code that is derived from its AWS Region code followed by a letter in sequential order. Below is a list of Availability Zones in the regions with the most services as of October 2023. It’s important to note that the list below doesn’t include all the Availability Zones in AWS.

Region Name | Availability Zones
US East (N. Virginia) | us-east-1a, us-east-1b, us-east-1c, us-east-1d, us-east-1e, us-east-1f
US West (Oregon) | us-west-2a, us-west-2b, us-west-2c, us-west-2d
Asia Pacific (Tokyo) | ap-northeast-1a, ap-northeast-1b, ap-northeast-1c, ap-northeast-2d
Europe (Frankfurt) | eu-central-1a, eu-central-1b, eu-central-1c
Europe (Ireland) | eu-west-1a, eu-west-1b, eu-west-1c

How to choose an AWS Availability Zone

Selecting an Availability Zone may appear simple once you’ve chosen your ideal AWS Region(s). Sometimes, people choose one at random. While it might work occasionally, there are particular circumstances where choosing zones calls for greater caution.

The most critical decision is how many AZs to use for your deployment, not which specific AZs to choose. AWS recommends deploying services in multiple AZs to achieve fault tolerance and resiliency benefits.

The number of AZs you need depends on the mission-criticality of your application. If your application needs 24/7 availability and reliability (e.g., applications in the healthcare and finance sectors), then you should use three or more AZs. This will minimize downtime in the event of a failure in one AZ.

Also, consider that some applications or tasks don’t benefit from multiple AZs. One example is CI/CD pipelines, which cost more when transferring large files through multiple AWS zones.

Above all, remember to carefully weigh performance and cost considerations while determining how many AZs you’ll need.

What are the key differences between AWS Regions and Availability Zones?

AWS Regions and Availability Zones are fundamental components of the AWS global infrastructure, each serving distinct but interconnected purposes. However, for those new to the realm of cloud-native applications development or even seasoned professionals, differentiating between these two concepts can often be puzzling. While both contribute to the robustness and resilience of AWS infrastructure, they serve distinct purposes in ensuring high availability, fault tolerance, and scalability.

Here are the key differences between AWS Regions and Availability Zones:

1. Geographical scope

AWS Regions are large and widely dispersed into separate geographic locations, meaning regions are located in different countries and continents.

AWS Availability Zones are distinct locations within an AWS Region. AZs are typically located within a few miles of each other, but they are isolated from each other to protect against failures in one AZ.

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2. Use case

AWS Regions are chosen based on factors like data residency requirements, compliance regulations, and the proximity to end-users.

Availability Zones are used to build highly available and fault-tolerant applications by distributing workloads across multiple zones within a region.

3. Fault isolation

Each AWS Region is isolated from the other regions, which means that a failure in one region will not affect others.

Each AZ is isolated from the other AZs within the same region. But if all the AZs in a region fail, the entire region fails.

4. Deployment flexibility

AWS Regions provide the flexibility to deploy resources across different geographic locations, enabling multi-region deployment.

Availability Zones support the deployment of applications and data within a specific geographic area to ensure low-latency access and data locality.

Enhancing Reliability Through Low Latency Performance

Low latency is critical in all industries, especially in sectors where real-time data processing and communication are paramount. A one-second delay can result in huge financial losses. While deploying your application in multiple regions and availability zones can help you achieve low latency, complex AWS environments can be challenging and AWS regions can fail.

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