Certopolis

AWS Certified Cloud Practitioner

AWS Regions vs Availability Zones vs edge locations explained

A Region is a physical location in the world where AWS clusters data centers, and each Region has at least three Availability Zones. An Availability Zone is one or more data centers with its own power, networking and connectivity, physically separate from the other zones in its Region. Edge locations are separate sites that Amazon CloudFront uses to cache content close to users.

Regions

Each AWS Region contains a minimum of three Availability Zones that are isolated and physically separate within one geographic area. AWS lists 34 Regions for a standard AWS account.

You choose a Region for each workload. AWS suggests picking one that has the services and features you need and one close to most of your users, to lower latency. You might also choose a Region to meet legal requirements.

Data stays where you put it. For example, Amazon S3 objects stored in a Region never leave that Region unless you explicitly transfer or replicate them to another Region.

Regions introduced after March 20, 2019 must be enabled before you can use them. Earlier Regions are enabled by default.

Availability Zones

An Availability Zone (AZ) is one or more discrete data centers with separate and redundant power, networking and connectivity. AZs in a Region are many kilometers apart, but within 100 km (60 miles) of each other.

The zones are linked by high-bandwidth, low-latency networking over redundant, dedicated metro fiber. AWS states this is fast enough for synchronous replication between zones.

AWS keeps zones from failing together. Generators and cooling equipment are not shared across zones and are designed to be supplied by different power substations. When AWS deploys updates to its services, deployments to the zones in one Region are separated in time.

Running your application in more than one AZ protects it from the failure of a single location. To survive a problem affecting a whole Region, you need a copy in a second Region.

Edge locations and Amazon CloudFront

Amazon CloudFront speeds up delivery of web content, such as HTML, CSS, JavaScript and image files. It delivers content through a worldwide network of data centers called edge locations.

A user's request goes to the edge location with the lowest latency. If the content is already cached there, CloudFront delivers it immediately. If not, CloudFront gets it from the origin you defined, such as an Amazon S3 bucket or a web server, which holds the definitive version.

By default, a cached file stays in an edge location for 24 hours before it expires. Because copies are held in many edge locations, you also get better reliability and availability.

Where the exam catches people

  • Believing a Region is a single data center: each Region has at least three Availability Zones, and each zone is one or more data centers.
  • Believing Availability Zones share power to stay in sync: generators and cooling are not shared, and zones are designed to be supplied by different substations.
  • Believing AWS updates every zone in a Region at once: deployments to zones in the same Region are separated in time.
  • Believing data is copied to other Regions automatically: S3 objects, for example, never leave their Region unless you transfer or replicate them.
  • Believing edge locations are where you run your EC2 instances: edge locations are where CloudFront caches content close to viewers.

Written from Amazon Web Services's documentation

Try 3 questions on this

Pick an answer to see why each option is right or wrong.

  1. Which of the following describe the design of every AWS Region? (Select TWO.)

    Right. In the game that’s Renown for your Cloud Technology and Services building.

    Not that one: B,D is right. In the game your Cloud Technology and Services building would lose a little Renown, and this question would come back later.

    Written from aws.amazon.com/about-aws/global-infrastructure/regions_az/

  2. Which of the following describe how AWS operates the Availability Zones within one AWS Region? (Select TWO.)

    Right. In the game that’s Renown for your Cloud Technology and Services building.

    Not that one: B,D is right. In the game your Cloud Technology and Services building would lose a little Renown, and this question would come back later.

    Show the full explanation and doc quotes

    It also says common points of failure such as generators and cooling equipment are not shared across Availability Zones.

    Written from docs.aws.amazon.com/whitepapers/latest/aws-fault-isolation-boundaries/availability-zones.html

  3. Which AWS service would deliver cached copies of web content to viewers from nearby edge locations?

    Right. In the game that’s Renown for your Cloud Technology and Services building.

    Not that one: B is right. In the game your Cloud Technology and Services building would lose a little Renown, and this question would come back later.

    Written from docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/Introduction.html