High Availability refers to the ability of an application to remain operational, even during component failures or outages. In the context of EC2, this means architecting your infrastructure to survive the failure of an instance, a rack, or even an entire Availability Zone (AZ).

Key Strategies for HA

1
Redundancy: Running multiple instances across different AZs.
2
Health Checks: Automatically detecting and replacing unhealthy instances via Auto Scaling.
3
Load Balancing: Using ELB to distribute traffic across healthy, available instances.
4
Data Replication: Ensuring data (like EBS snapshots or database replicas) is synchronized across AZs.