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Difficulty: Very hardAWS Global Infrastructure

A startup is deploying a critical database on AWS and is evaluating options for high availability and disaster recovery. The database must be resilient to localized physical events such as fires, earthquakes, or power grid failures in a metropolitan area, but the data must not leave the host country due to legal compliance. A developer suggests deploying a primary database instance in one AWS Region and a read replica in a different AWS Region within the same country, while another suggestion is to deploy the database across multiple Availability Zones within a single AWS Region. Which of the following statements correctly evaluates these proposals in the context of AWS Global Infrastructure design principles?

  1. A
    Deploying across multiple Regions is required to protect against localized physical events like fires or power outages, because all Availability Zones within a single Region share the same physical data center facilities and utility connections.
  2. B
    Deploying a read replica in an Edge Location in a different city provides the best low-latency failover and disaster recovery, as Edge Locations are fully functional regional data centers designed to host primary database workloads.
  3. Deploying across multiple Availability Zones in a single Region provides protection against localized physical events because Availability Zones are physically separated, isolated locations with independent power, cooling, and network connectivity, whereas deploying across different Regions introduces higher latency and is typically used for broader geographic disaster recovery.Answer
  4. D
    Deploying across multiple Availability Zones does not guarantee data residency within the host country, as Availability Zones within a single Region are often located in different neighboring countries to maximize geographic separation.

Answer

Deploying across multiple Availability Zones in a single Region provides protection against localized physical events because Availability Zones are physically separated, isolated locations with independent power, cooling, and network connectivity, whereas deploying across different Regions introduces higher latency and is typically used for broader geographic disaster recovery.
Deploying across multiple Availability Zones in a single Region provides high availability and fault tolerance against localized physical events because each Availability Zone is a physically isolated location with independent power, cooling, and networking. Because they are in the same Region, they are close enough to allow low-latency synchronous replication, while remaining in the same country to satisfy data residency regulations.

Step-by-Step Solution

1
Analyze the requirement for resilience against localized physical events within a metropolitan area.
Identify that the system requires physical isolation with independent power, cooling, and network infrastructure.
This ensures that a localized failure (like a power outage or fire) in one facility does not cause a secondary failure in another facility.
2
Evaluate the physical separation of AWS Availability Zones (AZs).
Confirm that AZs are physically isolated locations within an AWS Region, engineered to be fault-isolated.
Deploying the database across multiple AZs meets the localized resilience requirement without crossing regional boundaries.
3
Evaluate the requirement for data residency within the host country.
Verify that an AWS Region is situated within a single country's borders, and its AZs are located in the same country.
This guarantees that data stays within the national borders, fulfilling the compliance requirement.
4
Compare the AZ deployment with cross-Region and Edge Location options.
Determine that cross-Region deployment increases latency and is for disaster recovery, while Edge Locations cannot run databases.
This validates that the multi-AZ single-Region approach is the only proposal that satisfies all constraints.

Key Concept

Physical isolation and logical boundaries of AWS Regions, Availability Zones, and Edge Locations.
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Topics

AWS Global Infrastructure

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