Explanation

Amazon CloudWatch is the correct AWS service for collecting performance metrics from Amazon RDS instances and Amazon EC2 instances.

Why Amazon CloudWatch?

• Performance Monitoring: CloudWatch is specifically designed for monitoring AWS resources and applications
• Metrics Collection: It automatically collects metrics from EC2 instances (CPU utilization, network traffic, disk activity) and RDS instances (CPU, memory, storage, database connections)
• Real-time Monitoring: Provides real-time monitoring and alerting capabilities
• Custom Metrics: Supports custom metrics for application-specific monitoring

Why not the other options?

• AWS CloudTrail: Used for auditing API calls and user activity, not performance metrics
• Amazon Inspector: Security assessment service for vulnerability scanning, not performance monitoring
• AWS Config: Tracks resource configuration changes and compliance, not performance metrics

CloudWatch is the primary AWS service for collecting, analyzing, and responding to system-wide performance metrics across AWS services.