AWS Certified Solutions Architect - Associate
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A company hosts an online shopping application that stores all orders in an Amazon RDS for PostgreSQL Single-AZ DB instance. Management wants to eliminate single points of failure and has asked a solutions architect to recommend an approach to minimize database downtime without requiring any changes to the application code.
Which solution meets these requirements?
Other
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UAnonymous
A
Convert the existing database instance to a Multi-AZ deployment by modifying the database instance and specifying the Multi-AZ option.
B
Create a new RDS Multi-AZ deployment. Take a snapshot of the current RDS instance and restore the new Multi-AZ deployment with the snapshot.
C
Create a read-only replica of the PostgreSQL database in another Availability Zone. Use Amazon Route 53 weighted record sets to distribute requests across the databases.
D
Place the RDS for PostgreSQL database in an Amazon EC2 Auto Scaling group with a minimum group size of two. Use Amazon Route 53 weighted record sets to distribute requests across instances.
Explanation:
Explanation
Correct Answer: A
Why Option A is correct:
- Minimizes database downtime without application code changes: Converting an existing Single-AZ RDS instance to Multi-AZ is a seamless operation that requires no application code changes. During the conversion, RDS automatically creates a standby replica in a different Availability Zone.
- Eliminates single points of failure: Multi-AZ deployment provides high availability by maintaining a synchronous standby replica in another AZ. If the primary database fails, RDS automatically fails over to the standby with minimal downtime (typically 60-120 seconds).
- No application changes needed: The connection endpoint remains the same, so applications continue to use the same DNS name without modification.
Why other options are incorrect:
Option B: While this creates a Multi-AZ deployment, it requires manual snapshot/restore operations which involve downtime during the cutover and requires application configuration changes to point to the new database endpoint.
Option C: Read-only replicas are asynchronous and cannot be used for failover of write operations. They are designed for read scaling, not high availability. Route 53 weighted record sets would not properly handle failover scenarios for write operations.
Option D: RDS databases cannot be placed in EC2 Auto Scaling groups. RDS is a managed service separate from EC2 instances. This approach misunderstands how RDS works and would not provide the required high availability.
Key AWS Concepts:
- RDS Multi-AZ: Provides high availability through synchronous replication to a standby instance in another AZ
- Automatic failover: RDS automatically detects failures and promotes the standby to primary
- Zero application changes: The DNS endpoint remains unchanged during failover
- Single-AZ to Multi-AZ conversion: A simple modification operation in the RDS console or CLI
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