AWS Certified Solutions Architect - Associate
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A company moved its on-premises PostgreSQL database to an Amazon RDS for PostgreSQL DB instance. The company successfully launched a new product. The workload on the database has increased. The company wants to accommodate the larger workload without adding infrastructure.
Which solution will meet these requirements MOST cost-effectively?
Other
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UAnonymous
A
Buy reserved DB instances for the total workload. Make the Amazon RDS for PostgreSQL DB instance larger.
B
Make the Amazon RDS for PostgreSQL DB instance a Multi-AZ DB instance.
C
Buy reserved DB instances for the total workload. Add another Amazon RDS for PostgreSQL DB instance.
D
Make the Amazon RDS for PostgreSQL DB instance an on-demand DB instance.
Explanation:
Explanation
Correct Answer: A
Why Option A is correct:
- Vertical scaling (making the DB instance larger) is the most cost-effective way to handle increased workload without adding infrastructure. By upgrading to a larger instance type (more CPU, memory, and I/O capacity), you can accommodate higher loads.
- Buying reserved instances provides significant cost savings (up to 72% compared to on-demand pricing) for predictable workloads.
- This approach avoids the complexity and additional costs of managing multiple DB instances while providing immediate capacity increase.
Why other options are incorrect:
Option B (Multi-AZ DB instance):
- Multi-AZ deployment provides high availability and disaster recovery by maintaining a standby replica in another Availability Zone.
- While it improves resilience, it doesn't directly address performance scaling and actually increases costs by requiring a standby instance.
Option C (Add another DB instance):
- Adding another DB instance means horizontal scaling, which requires application changes to implement read replicas or sharding.
- This adds infrastructure (against requirements) and increases management complexity.
- Even with reserved instances, maintaining multiple instances is more expensive than scaling up a single instance.
Option D (On-demand DB instance):
- Switching to on-demand pricing is actually more expensive than reserved instances for predictable workloads.
- This doesn't address the performance scaling requirement - it only changes the billing model.
Key AWS Concepts:
- Amazon RDS Scaling: Vertical scaling (instance size) vs. horizontal scaling (read replicas)
- Pricing Models: Reserved Instances (for predictable workloads) vs. On-Demand (for variable workloads)
- Cost Optimization: Right-sizing instances and using reserved capacity for predictable workloads
Best Practice: For predictable workload increases, scale vertically first (larger instance) with reserved instances for cost savings, then consider read replicas for read-heavy workloads if needed.
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