Spring Cloud Research & Evidence-Based Practice 4

Question 1

A developer wants to validate that Spring Cloud Feign retry logic does not retry non-idempotent POST requests. What is the evidence-based recommended approach?

Accepted Answer

Configure a custom Retryer that retries only on connection errors and limits retries to idempotent HTTP methods

Answer

A custom Retryer restricts retries to safe scenarios (idempotent methods, connection-level failures), preventing duplicate side effects from retried POST requests.

Question 2

Empirical studies on distributed configuration management recommend which strategy to reduce risk when rolling out a Spring Cloud Config change across a large fleet?

Accepted Answer

Use canary deployment: push the config change to a small subset of instances first, monitor error rates, then expand

Answer

Canary rollout of configuration changes limits blast radius — if the new configuration causes errors, only a small fraction of traffic is affected before rollback.

Question 3

When sizing Resilience4j TimeLimiter timeout values for Feign-based Spring Cloud calls, what does evidence-based guidance recommend?

Accepted Answer

Derive the timeout from the p99 response time of the upstream service under normal load, plus a small buffer

Answer

Basing the timeout on the observed p99 latency plus a small buffer ensures legitimate slow-but-valid requests succeed while genuinely hung calls are cancelled promptly.

Question 4

Research into Spring Cloud Sleuth's compatibility with virtual threads (Project Loom) in Java 21+ highlights which key concern?

Accepted Answer

ThreadLocal-based trace context propagation used by Sleuth is not automatically inherited by virtual threads, requiring explicit context passing

Answer

Sleuth relies on ThreadLocal for trace context; virtual threads don't automatically inherit parent thread locals, so Micrometer Tracing's context propagation model must be adopted.

Question 5

A case study on Spring Cloud Gateway rate limiting with Redis reveals over-limiting spikes during Redis leader election. What is the most resilient evidence-based remediation?

Accepted Answer

Use Redis Cluster with Sentinel and implement a fail-open fallback that allows requests when Redis is unavailable

Answer

Redis Cluster with Sentinel improves availability, and a fail-open policy during Redis downtime prevents legitimate traffic from being blocked by infrastructure events.

Spring Cloud Practice Test

Spring Cloud Practice Test

Spring Cloud Research & Evidence-Based Practice 4