25 interview questions on RAG, embeddings, tool calling, MCP, agents, evaluation and cost control for Java developers, with short answers in accordions and runnable proof for the tricky ones.
Kafka share groups (KIP-932) let many consumers share one partition and acknowledge records one by one. Measured against a real Kafka 4.3.1 broker with Spring Kafka 4.1.1: what you gain, what you lose, and when RabbitMQ is still the answer.
Spring Cloud 2026.0.0-M1 adds an HTTP notifier to Config Server and fixes how Gateway handles forwarded headers from untrusted proxies. I ran both and show what changes and what to test now.
Jev is a hosted TypeSafe AI API that answers yes/no, pick-one and score questions about your data. Here is the Spring AI starter, how to wire it, and a confidence-gated model router, verified offline.
Package an agent's know-how as SKILL.md folders and let Spring AI load them on demand with one tool. What the model sees, what a load costs, and the edge cases I reproduced.
Spring AI 2.1.0-M1 adds VectorStore.upsert() that takes vectors you already have. Here is what it does, which stores support it, and how to move between stores without calling the embedding model again.
Spring AI 2.1.0-M1 can talk to OpenAI's Responses API. One property switches the model bean, and new options add hosted web search, code interpreter and remote MCP. What I verified, what I could not measure.
Spring AI 2.1.0-M1 models an assistant turn as an ordered list of parts. Here is what the model looks like, how streaming marks partial parts, and where reasoning is silently lost today.
A Spring Boot 4.1 service started 3.9 s on a plain JDK 25 and 2.0 s with the JDK AOT cache, from one extra flag. Measured against AppCDS, Spring AOT and a GraalVM native image, with 24 ways the cache gets silently rejected (rebuilt jar, copied files, ZGC, compact headers), the Docker consequences, and what is and is not known about Netflix's production use.
Measured jlink results on Temurin 25 for a real Spring Boot 4.1 app: which modules it needs (jdeps), what each jlink option saves, why java.desktop costs 15 MB, a failure when you remove it, and a JMOD-based custom runtime of 42 MB for a minimal modular program. Docker was not available, so no image sizes are claimed.