What is fault tolerance in the context of applications?

Fault tolerance in the context of applications refers to the ability of a system to continue functioning even when some of its components fail. This is achieved through built-in redundancy. Redundancy may involve duplicating critical components, such as servers, data paths, or processes, that allow the application to maintain its functionality despite the failure of one or more of those components. If a failure occurs, the system can reroute tasks or request services from backup resources, ensuring that users experience minimal disruption. This capability is crucial for applications that require high availability and reliability, such as those used in finance, healthcare, and critical infrastructure.

In contrast, enhancing application performance during high demand focuses on scalability rather than resilience. The process of restoring service after an outage emphasizes recovery and does not inherently prevent an outage from affecting application operations. Balancing application load for efficiency pertains to optimizing resource usage rather than ensuring operational continuity during failures. Therefore, the definition of fault tolerance is best captured by the concept of built-in redundancy that allows for ongoing operation under adverse conditions.