Q16 — AWS SAA-C03 Ch.15

Question 16 of 100 | ← Chapter 15

Q1116. A company hosts a stateless web application with low data storage in a single AWS Region. The company wants to increase the resiliency of the application to include a multi-Region presence. The company wants to set the recovery time objective (RTO) and recovery point objective (RPO) to hours. The company needs a low-cost and low-complexitydisaster recovery (DR) strategy.Which DR strategy should the company use?

Correct Answer: B. Pilot light

Explanation

To determine the best disaster recovery (DR) strategy for the company's requirements, let's analyze the given constraints and evaluate each option:Requirements:Multi-Region presence: The application must be resilient across multiple AWS Regions. RTO and RPO in hours: The Recovery Time Objective (RTO) and Recovery Point Objective (RPO) can be measured in hours (not seconds or minutes).Low-cost and low-complexity: The DR strategy should be inexpensive and easy to implement.Key Considerations:RTO and RPO:RTO is the maximum acceptable downtime after a disaster.RPO is the maximum acceptable data loss after a disaster.Hours-level RTO/RPO implies that the application can tolerate some downtime and data loss, which allows for simpler and cheaper DR strategies.Multi-Region Resiliency:The application must be able to fail over to another Region if the primary Region fails.Stateless Web Application:Since the application is stateless, there is no need to synchronize in-memory state between Regions (only data storage needs to be considered).Low Data Storage:The application has minimal data storage, which simplifies data replication.Evaluation of DR Strategies:A. Warm StandbyDescription: A partially deployed copy of the application runs in a secondary Region at reduced capacity (e.g., fewer instances). In a disaster, the secondary Region is scaled up to handle full traffic.Pros:Faster recovery (RTO in minutes to hours) compared to backup and restore. Data is continuously replicated to the secondary Region (low RPO).Cons:Higher cost than backup and restore (due to running resources in the secondary Region). Moderate complexity (requires scaling logic and monitoring). Fit: Not the best for "low-cost" since resources are running continuously.B. Pilot LightDescription: A minimal version of the application (e.g., database, compute, and networking) is pre-deployed in a secondary Region. In a disaster, the secondary Region is scaled up to handle full traffic.Pros:Faster recovery than backup and restore (RTO in hours).Data is replicated to the secondary Region (low RPO).Lower cost than warm standby (only minimal resources are running).Cons:Slightly higher complexity than backup and restore (requires pre-deployment of some infrastructure).Fit: Good balance of cost, complexity, and recovery time.C. Backup and RestoreDescription: The application and data are backed up periodically (e.g., daily) to a secondary Region. In a disaster, the backups are restored to a new environment in the secondary Region.Pros:Lowest cost (no running resources in the secondary Region). Simplest to implement (no continuous replication or scaling logic).Cons:Higher RTO (hours to days, depending on backup frequency and restore time).Higher RPO (data loss up to the last backup interval).Fit: Not ideal for RTO/RPO in hours (restore time could exceed hours, and data loss could be unacceptable).D. Multi-Site Active-ActiveDescription: The application runs simultaneously in multiple Regions, with traffic distributed across them (e.g., via DNS or load balancer). In a disaster, traffic is automatically redirected to the surviving Regions.Pros:Fastest recovery (RTO in seconds to minutes).Lowest RPO (no data loss, as all Regions are in sync).Cons:Highest cost (resources running in all Regions at full capacity). Highest complexity (requires synchronization, conflict resolution, and traffic management). Fit: Not suitable for "low-cost" or "low-complexity" requirements.Conclusion:Given the requirements for low-cost, low-complexity, and RTO/RPO in hours, the Pilot Light strategy is the best fit. Here's why:It is cheaper than Warm Standby (only minimal resources are running in the secondary Region). It is simpler than Multi-Site Active-Active (no full-time synchronization or traffic distribution). It meets the RTO/RPO requirements (RTO in hours due to scaling up the pilot light, and RPO is low because data is replicated to the secondary Region).Final 答案:B (Pilot light)