Drills

How do you configure and debug CORS in Spring MVC?

Configures finite origins, methods, headers, credentials, and preflight behavior while separating browser enforcement from authorization.

Architecture scenarioMedium~7 min

How do you decide between Spring Data repository methods, projections, and custom repository code?

Uses generated repository behavior for simple cases and explicit query or implementation boundaries when the use case becomes complex.

How do you design an ExecutorService for a Java backend?

Designs executor ownership, pool size, queue capacity, rejection, shutdown, task context, and observability around workload behavior.

Java

How do you diagnose a missing or ambiguous Spring bean?

Traces the injection point, candidate type, registration path, conditions, profiles, generics, qualifiers, and package boundaries.

How do you diagnose and fix an N+1 query problem in Hibernate?

Finds repeated association queries with SQL evidence and chooses a bounded fetch or projection without creating a cartesian result.

Debugging scenarioHard~15 min

How do you diagnose and fix blocking work on an asyncio event loop?

Finds synchronous I/O or CPU work that prevents the event loop from scheduling other tasks.

How do you diagnose a request rejected before a Spring controller runs?

Classifies mapping, conversion, binding, validation, multipart, CORS, filter, and negotiation failures before changing controller code.

Debugging scenarioHard~15 min

How do you diagnose a request that never reaches the FastAPI path operation?

Locates pre-handler failures across proxies, routing, parsing, validation, dependencies, and middleware using structured evidence.

FastAPIPydanticPython

How do you diagnose event-loop stalls, orphaned tasks, and async resource leaks?

Combines asyncio debug evidence, task inspection, warnings, profiling, and capacity signals.

Architecture scenarioMedium~7 min

How do you diagnose Java classpath and linkage errors?

Distinguishes missing-class and incompatible-class failures, then traces them to the actual packaged runtime dependency graph.

Java

How do you distinguish missing fields from explicit nulls in a FastAPI PATCH endpoint?

Models partial updates without confusing omitted fields, explicit nulls, defaults, or unauthorized changes.

FastAPIPydanticPython

How do you evolve and version a Spring MVC API?

Prefers compatible evolution, uses Spring version resolution when a breaking contract requires it, and operates deprecation deliberately.

How do you expose pagination, filtering, and sorting safely in a Spring API?

Maps a bounded public list contract to Spring arguments without exposing persistence property names or unstable ordering.

Debugging scenarioMedium~7 min

How do you handle 401 versus 403 responses in Spring Security?

Separates authentication challenge from denied authorization and traces the selected entry point, denied handler, and matched rule.

How do you handle circular dependencies between Spring beans?

Treats a bean cycle as a design signal, explains constructor failure, and uses delayed resolution only for genuine lifecycle boundaries.

How do you handle exceptions and partial results from several asyncio tasks?

Defines fail-fast, all-results, and partial-success behavior for concurrent asyncio operations.

How do you implement global API error handling with @ControllerAdvice and ProblemDetail?

Maps known framework and application failures to RFC 9457 responses while preserving stable codes, safe detail, and correlation.

How do you keep FastAPI's generated OpenAPI document stable and useful as a contract?

Controls operation identities, request and response schemas, error documentation, and compatibility checks without hand-maintaining a second contract.

FastAPIPydanticPython

How do you limit concurrent asyncio calls without creating unbounded work?

Places semaphore and admission boundaries around scarce work without retaining unlimited tasks.

Architecture scenarioMedium~7 min

How do you make a Python application's dependencies reproducible?

Connects virtual environments, pyproject metadata, version constraints, lock artifacts, Python versions, and CI verification.

How do you make large JPA write batches efficient and safe?

Combines JDBC batching, compatible identifiers, periodic flush and clear, bounded transactions, and explicit bulk-operation semantics.

How do you make Python dependency and container builds reproducible?

Produces a pinned, reviewable Python artifact once and promotes the same image across environments.

How do you map domain failures to HTTP responses in a Spring API?

Keeps domain outcomes transport-neutral and maps not-found, conflict, invalid transition, and dependency failure at the web boundary.