The Healthcare Appointment Booking System is a secure, highly available cloud-based application that allows patients to book, cancel, and manage appointments with doctors. The backend is implemented with Flask running on Auto Scaling EC2 instances in private subnets behind an Application Load Balancer (ALB), while the database uses Amazon RDS (Postgres/MySQL) Multi-AZ for high availability and automated backups. The frontend is served via S3 + CloudFront for fast, global access, and security is enforced through IAM least-privilege roles, private networking, and encrypted data in transit and at rest, making the system HIPAA-ready. Operational excellence is ensured with CloudWatch logs, metrics, and alarms, while SSM Session Manager provides secure access to private instances without public IPs. The infrastructure is automated using Terraform or CloudFormation, and CI/CD pipelines enable safe and fast deployment. Production KPIs include 99.95% uptime, sub-200ms latency under moderate load, and automatic recovery of unhealthy instances, making the system reliable, scalable, and secure for real-world healthcare use.