Definition
High availability (HA) refers to the design of systems and applications to ensure continuous operation and minimize downtime, even in the face of component failures. It is achieved through redundancy, where critical components have backups ready to take over immediately if the primary fails. This resilience is crucial for maintaining business continuity and user trust by preventing service interruptions. For instance, a web server cluster with multiple identical servers behind a load balancer ensures that if one server goes down, others continue serving requests. High availability differs from disaster recovery, which focuses on recovering from major catastrophic events, whereas HA addresses more localized or component specific failures. Understanding HA is essential for cloud architecture, security, and project management certifications like AWS Solutions Architect Associate and CISSP.