Spring Cloud Core Knowledge Summary and High‑Frequency Interview Questions

Today we share a collection of high‑frequency Spring Cloud interview questions, starting with a brief definition of Spring Cloud as a Spring‑Boot‑based framework that simplifies integration with external systems and supports short‑lived microservice tasks.

Microservices are described as independently deployable services that communicate via lightweight protocols such as HTTP/REST or asynchronous messaging (e.g., RabbitMq , ActiveM , Kafka ).

Key advantages of Spring Cloud include handling distributed system complexities, service discovery, redundancy, load balancing, performance, and deployment challenges.

Service communication can be synchronous (Dubbo RPC, Spring Cloud REST) or asynchronous via message queues.

Service circuit breaking and degradation are explained, with Hystrix annotations like @EnableHystrix and @HystrixCommand(fallbackMethod="XXX") providing fallback methods when a service fails or times out.

The differences between Eureka (AP, high availability) and Zookeeper (CP) are highlighted, along with Eureka’s self‑protection mechanism that prevents premature deregistration during network issues.

Spring Boot focuses on rapid development of individual microservices, while Spring Cloud provides global governance features such as configuration management, service discovery, circuit breaking, routing, and event bus.

Load balancing concepts are covered, emphasizing resource optimization and fault tolerance.

Hystrix’s role as a latency and fault‑tolerance library is detailed, including its thread‑pool isolation and fallback strategies.

RPC implementation basics are outlined: network connection handling, serialization/deserialization, and client‑server proxy generation.

Service registration is performed via Eureka or Zookeeper using annotations like @EnableEurekaServer and @EnableDiscoveryClient , with Ribbon or Feign handling client‑side calls.

Ribbon is introduced as a load‑balancing client (integrated into Feign by default), while Feign is a declarative HTTP client that simplifies API calls and supports integration with Ribbon and Hystrix.

Differences between Ribbon and Feign are summarized: annotation usage, service specification location, and invocation style.

The core Spring Cloud components—Eureka, Feign, Ribbon, Hystrix, and Zuul—are listed.

Spring Cloud Bus is described as a lightweight message‑broker that propagates configuration changes across distributed nodes.

Spring Cloud Config provides centralized configuration management, supporting both local files and remote Git repositories.

Spring Cloud Gateway, the second‑generation gateway replacing Zuul, offers routing, authentication, and rate‑limiting capabilities via a RouteLocatorBuilder bean.