High availability is the academic concept and research area focused on the design, implementation, and evaluation of systems engineered to minimize downtime and ensure continuous service provision in the face of localized failures or faults. It investigates strategies for fault tolerance, redundancy mechanisms, and rapid system recovery, characterizing systems by their ability to maintain operations and accessibility despite disruptions. The significance of high availability lies in ensuring the dependability and continuous operation of critical services, thereby contributing fundamentally to overall system resilience and trustworthiness.