High Availability
High Availability (HA) is a system design approach that aims to ensure an agreed level of operational performance, usually uptime, for a higher than normal period. It involves implementing redundant components and failover mechanisms to minimize downtime and maintain service continuity in the event of hardware failures, software crashes, or other disruptions. The goal is to provide continuous availability of services, often measured as a percentage of uptime (e.g., 99.999% or 'five nines').
Developers should learn and implement High Availability for critical applications where downtime can lead to significant financial losses, reputational damage, or safety risks, such as in e-commerce platforms, banking systems, healthcare services, and telecommunications. It is essential in cloud-native and distributed systems to handle failures gracefully, ensuring resilience and reliability, and is often required in service-level agreements (SLAs) to meet customer expectations for uninterrupted access.