Spring Cloud Case Studies & Practical Application 3

Question 1

A healthcare API gateway must enforce JWT authentication for all downstream services without modifying each service. Which Spring Cloud Gateway capability handles this centrally?

Accepted Answer

Global filters applying a custom JWT validation filter

Answer

A Global GatewayFilter applied to all routes can validate JWTs at the gateway boundary before forwarding requests, keeping downstream services auth-agnostic.

Question 2

After enabling Spring Cloud Sleuth, a team finds trace IDs are not propagating through Kafka messages between services. What must they add?

Accepted Answer

Spring Cloud Sleuth Kafka binder instrumentation or Micrometer Tracing Kafka propagation

Answer

Sleuth/Micrometer Tracing requires messaging-specific instrumentation to inject and extract trace context in Kafka message headers.

Question 3

A SaaS platform serves multiple tenants, each needing isolated configuration. How can Spring Cloud Config Server support per-tenant configuration?

Accepted Answer

Use profile-based naming (e.g., application-{tenant}.yml) with tenant profile activation

Answer

Config Server resolves files by application name and profile, so naming files with tenant identifiers as profiles enables clean per-tenant configuration isolation.

Question 4

A team's Feign client calls fail intermittently due to transient network issues. They want automatic retries only on idempotent GET requests. How should they configure this?

Accepted Answer

Configure a Feign Retryer or Resilience4j Retry with a custom predicate excluding non-idempotent methods

Answer

A custom Resilience4j Retry predicate or Feign Retryer can be scoped to idempotent operations, avoiding dangerous duplicate side effects on POST/PUT.

Question 5

A company migrates from Zuul 1 to Spring Cloud Gateway. Their Zuul filters used blocking I/O with ThreadLocal. What must developers change?

Accepted Answer

Replace ThreadLocal state with reactive context (Reactor Context) since Gateway is non-blocking

Answer

Spring Cloud Gateway is built on Project Reactor and Netty (non-blocking), so ThreadLocal-based state does not propagate across async boundaries and must be replaced with Reactor Context.

Spring Cloud Practice Test

Spring Cloud Practice Test

Spring Cloud Case Studies & Practical Application 3