High Availability
High Availability (HA) is a system design approach that aims to ensure an agreed level of operational performance, typically uptime, by minimizing downtime and service interruptions. It involves implementing redundant components, failover mechanisms, and fault tolerance to maintain continuous service availability, often measured as a percentage of uptime (e.g., 99.999% or 'five nines'). This concept is critical in environments where system failures can lead to significant financial loss, safety risks, or reputational damage.
Developers should learn and implement High Availability when building systems that require minimal downtime, such as e-commerce platforms, financial services, healthcare applications, or critical infrastructure. It is essential for ensuring business continuity, meeting service-level agreements (SLAs), and providing reliable user experiences, especially in cloud-native, distributed, or mission-critical applications where failures can have severe consequences.