AWS Certified Solutions Architect - Associate

Explanation

Correct Answer: D. Purchase a Capacity Reservation in the failover Region.

Why this is correct:

1. Capacity Reservation is specifically designed to guarantee EC2 capacity in a specific Availability Zone within a region. When designing a disaster recovery strategy, you need to ensure that when you fail over to the secondary region, you have guaranteed capacity available to launch your instances.

2. Capacity Reservation vs Other Options:

   • On-Demand Instances (Option A): While On-Demand instances provide flexible capacity, they don't guarantee availability. During a disaster scenario where many customers might be failing over to the same region, capacity could be limited.
   • EC2 Savings Plan (Option B): This provides cost savings but doesn't guarantee capacity. It's a pricing model, not a capacity guarantee.
   • Regional Reserved Instances (Option C): Regional RIs provide capacity discounts but only offer capacity priority, not guaranteed capacity. They can be applied across Availability Zones within a region but don't reserve specific capacity.

3. Disaster Recovery Requirements: For DR scenarios where you need to ensure you can launch instances in the failover region when needed, Capacity Reservation is the only option that provides actual capacity guarantees.

Key AWS Concepts:

• Capacity Reservation: Reserves capacity in a specific Availability Zone for any duration, ensuring you have EC2 capacity when you need it.
• Disaster Recovery Planning: Requires guaranteed capacity in the failover region to ensure business continuity.
• Regional vs Zonal: Capacity Reservation is zonal (specific AZ), while regional RIs provide flexibility across AZs but no capacity guarantee.

Best Practice: For critical DR scenarios, use Capacity Reservations in the failover region to ensure you have the necessary EC2 capacity available when you need to execute your failover plan.