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Difficulty: HardHigh Availability, Scalability, and Elasticity

An e-commerce company hosting its application on Azure has two primary requirements for its architecture:

* During flash sales, the system must automatically provision additional virtual machines to handle sudden, short-lived spikes in traffic, and automatically shut them down afterward to control costs.
* The application must remain online and accessible even if a power outage affects an entire physical building housing the servers in the primary Azure region.

Which combination of cloud concepts directly addresses these requirements?

  1. A
    Vertical scalability for adjusting compute power, and Disaster Recovery for replicating data to a secondary Azure region
  2. B
    Disaster Recovery for restoring backup images, and Elasticity for increasing the capacity of a single virtual machine
  3. Elasticity for the automatic scaling of compute instances, and High Availability for distributing resources across separate Availability ZonesAnswer
  4. D
    Horizontal scalability for manual resource provisioning, and High Availability for local hardware redundancy

Answer

Elasticity for the automatic scaling of compute instances, and High Availability for distributing resources across separate Availability Zones
The correct answer accurately identifies elasticity as the mechanism for automated, dynamic horizontal scaling to handle fluctuating transaction demand, and high availability (via separate Availability Zones) as the mechanism to maintain uptime during a physical building power outage within the primary region.

Step-by-Step Solution

1
Analyze the scaling requirement: handling unpredictable, short-lived spikes by dynamically adding and removing resources to minimize costs.
This matches the definition of cloud elasticity, which leverages automation to match resource allocation to real-time workload demands.
Elasticity differs from standard scalability by incorporating automation for both scaling out (adding instances) and scaling in (removing instances) dynamically.
2
Analyze the availability requirement: surviving a physical power outage affecting an entire server building within the primary region.
This matches high availability design, specifically using Azure Availability Zones to distribute redundant virtual machines across distinct physical datacenters.
Availability Zones provide isolation against datacenter failures within a region, ensuring continuous operation without resorting to disaster recovery replication to another region.

Key Concept

The distinction between high availability (local fault tolerance), elasticity (dynamic automatic scaling), and scalability (capacity modification).
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Topics

High Availability, Scalability, and Elasticity

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