▸case-18 To prevent breaking REST API changes between microservices in a Spring Boot environment, a developer suggested deploying all services simultaneously in a shared staging environment for manual regression testing. Which contract testing tool should be integrated into the Spring CI/CD pipeline? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-11 We want to define a domain interface `PaymentMethod` in Java 21 such that only `CreditCard`, `PayPal`, and `BankTransfer` are permitted to implement it, preventing any third-party subclassing. A developer suggested making the constructors package-private. How should this be declared in Java 21? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-03 We need to run two concurrent subtasks (fetching user profile and fetching order history) in Java 21 where if either fails, the entire operation should instantly cancel remaining tasks and throw an exception. A teammate suggested standard uncoordinated CompletableFuture.allOf(). What modern Java 21 preview feature should be used to manage this scoped lifecycle? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-23 We are developing an async Python microservice using FastAPI and SQLAlchemy with asyncio. Provide advice on optimizing Python's event loop and async database sessions. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-05 We are writing integration tests for a Spring Boot 3 repository layer. A developer proposed using an in-memory H2 database to execute SQL queries. How should we write tests against an actual PostgreSQL database instance in JUnit 5 without installing local services? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-04 In a Spring Boot 3 application with JPA, querying a list of 500 Customer entities causes 501 SQL queries to be executed to fetch their Orders. A developer suggested calling Hibernate.initialize() inside a loop. How should this query be optimized in Spring Data JPA? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-14 We are migrating a Spring Boot application to Spring Security 6. A pull request uses `WebSecurityConfigurerAdapter` and overrides `configure(HttpSecurity http)`. How should HTTP security rules be configured in modern Spring Security 6? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-13 We are developing a high-performance Java 21 application that needs off-heap memory allocation and native C library interoperability. A team member suggested using `sun.misc.Unsafe`. What standard, safe Java 21 LTS API should replace `Unsafe` for native memory access? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-07 We are building a modular monolithic application in Spring Boot 3 and want to enforce strict boundary assertions and architectural validation between domain modules at compile/test time. Developers suggested manually organizing packages into subfolders. Which Spring library should be used to structure and verify these modular boundaries? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-06 We need to add fault tolerance, rate limiting, and circuit breaking to our Spring Boot 3 microservices. A senior dev suggested adding Spring Cloud CircuitBreaker with deprecated Netflix Hystrix dependencies. Which modern resilience library should be integrated with Spring Boot 3? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-15 We suspect virtual threads in our Java 21 application are pinning carrier threads due to synchronized blocks during database access. A developer suggested setting -XX:+PrintGCDetails to detect virtual thread pinning. What JVM system property should be set to log stack traces when a virtual thread pins its carrier thread? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-12 We need to propagate trace IDs and span IDs across distributed Spring Boot 3 microservices and export them to OpenTelemetry endpoints. In Spring Boot 2, Spring Cloud Sleuth was used. What framework/library replaces Sleuth in Spring Boot 3? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-21 We are optimizing a C# .NET 8 Web API service handling high throughput using `async`/`await` and `ValueTask<T>`. Provide advice on configuring thread pool settings and task scheduling in .NET 8. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-17 We need version-controlled database schema migrations for a Spring Boot 3 application connected to PostgreSQL. A developer proposed manually running SQL scripts via psql before deployments. Which standard database migration library should be integrated with Spring Boot? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-08 We have a sealed hierarchy `sealed interface Response permits Success, Error`. `Success` is a record `record Success(String payload, int code)`. In Java 21, write a method `handleResponse(Response r)` using a switch expression that directly deconstructs `Success` into its `payload` and `code` variables without manual casting or getter calls. | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-22 We are building an enterprise REST API in Node.js with Express and TypeScript. We need guidance on configuring cluster module workers and event loop asynchronous processing in Node.js. | fail→pass | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-01 We are migrating a Spring Boot 3.2 REST service handling high-concurrency HTTP requests. Instead of manually configuring custom thread pool executors, how should we enable lightweight thread-per-request execution in application.properties? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-19 We need to expose application health, metrics, and environment details for Kubernetes readiness and liveness probes in Spring Boot 3. Which Spring Boot module provides these production-ready endpoints? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-02 Our financial trading API runs on Java 21 with a 32GB heap and requires sub-millisecond maximum GC pause times. Developers proposed using Parallel GC with heavy tuning. Which modern garbage collector should be configured instead? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-09 We need to compile a Spring Boot 3 REST API into a standalone native binary for near-zero startup time and lower memory footprint in Kubernetes. A teammate suggested using legacy GCJ or compiling ahead-of-time with standard javac. Which compiler distribution should be used with Spring Native / Spring Boot build plugins? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-10 We need a data carrier class in Java 21 to hold HTTP response metrics (`long durationMs`, `int statusCode`). A developer created a mutable JavaBean with 50 lines of boilerplate getters, setters, equals, hashCode, and toString. How should this data structure be defined concisely and immutably in Java 21? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-16 In Java 21, when passing immutable contextual data across virtual threads within a bounded operation execution, `ThreadLocal` introduces memory leak risks and mutability overhead. Which modern Java 21 feature should be used for lightweight, immutable context propagation? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |
▸case-20 We need to optimize the production database connection pool for a Spring Boot 3 service handling concurrent database transactions. A developer suggested using old Commons DBCP. What default, high-performance connection pool is built into Spring Boot? | fail→fail | — | — | — | — | — | — | — | — | — | — | — | — |