What is autoboxing in Java? What is a BlockingQueue and how does it work? What is the difference between HashSet and TreeSet? How does ConcurrentHashMap store data internally and ensure thread safety? What are Future and CompletableFuture? When should we use each? How do you create an ExecutorService object with a fixed thread pool size? What should we remember when overriding equals() in Java? What is the difference between Runnable and Callable beyond return type? What is the difference between java.io and java.nio? How does Garbage Collection (GC) work in Java? Are there any techniques? What is heap memory? Does GC operate on heap or non-heap memory? How can we get a heap dump in Java? In JPA, if a table has hundreds of columns and we don’t know which ones were updated (e.g., from a client payload), how can we detect the changes? How do we write custom queries in JPA? How do we make an entry in an audit table using a stored procedure? Which SQL command is used? What is the difference between UNION and UNION ALL? What are CLOB and BLOB in databases? What is the difference between @PathVariable and @RequestParam? If there are two beans of the same type in Spring Boot, how do we differentiate them? (Answer: using @Qualifier) How do we prevent fallback in Spring Boot? (Answer: Resilience4j/Hystrix) What is the name of the design pattern used for fallback? (Answer: Circuit Breaker) How do we maintain REST API versioning? What is the difference between containerized and VM-based environments? What is the custom extension for a Dockerfile? (e.g., .dockerfile) How do we squash multiple commits into a single commit in Git? Which Git command maintains history—merge, rebase, or another? (Answer: merge) What is the difference between a queue and a topic? What are common Kafka interview questions? (e.g., producers, consumers, partitions, offsets, delivery guarantees) If calling another API over HTTPS throws an SSL error saying the public key cert path is incorrect: What would you do? Where is the certificate typically stored? Which tool is used in an environment with hundreds of microservices to collect logs? (Answer: Splunk) Which tool is used to monitor memory and collect memory dumps? (Answer: Grafana, Prometheus) What is a Record in Java? In which scenario would you use it? What is JIT (Just-In-Time Compiler) in Java?