Spring Boot WebClient: Performance Optimization and Resilience

Spring WebClient is a reactive, non-blocking HTTP (HyperText Transfer Protocol) client designed for making requests to external services. It belongs to the Spring WebFlux framework and provides advanced, scalable handling of HTTP requests more efficiently than the RestTemplate. 

WebClient also supports parallel and reactive programming, making it suitable to perform a large volume of operations without blocking requests. It is ideal when you want to build high-performance applications, either by making external API calls or having thousands of concurrent requests.