Drills

When should you use pytest skip, xfail, or quarantine a test?

Distinguishes unavailable conditions, known defects, and unstable tests while keeping lost coverage visible.

pytestPython

Comparison questionMedium~7 min

When would you choose a comprehension or a generator expression in Python?

Compares eager collections with lazy one-pass generation through memory, timing, reuse, readability, and resource ownership.

Architecture scenarioMedium~10 min

When would you stream data instead of loading it all into memory?

Covers large exports, uploads, and API responses where bounded memory matters more than convenience.

.NETASP.NET CoreC#

When would you use a function-based or class-based Django view?

Chooses Django view style by clarity, reuse, and lifecycle needs rather than hierarchy preference.

Comparison questionHard~10 min

When would you use a Protocol instead of an abstract base class in Python?

Chooses structural or nominal contracts based on ownership, runtime identity, shared behavior, and third-party integration.

When would you use asyncio Lock, Event, Condition, or Semaphore?

Chooses task synchronization by protected state, notification predicates, and limited capacity.

Comparison questionHard~15 min

When would you use asyncio.TaskGroup or asyncio.gather()?

Compares structured task ownership with ordered result aggregation and different failure behavior.

Comparison questionHard~15 min

When would you use asyncio.to_thread() or run_in_executor()?

Compares convenient context-propagating thread offload with explicit executor selection and ownership.

When would you use Django select_related or prefetch_related?

Chooses Django relationship loading from relationship shape, result cardinality, and measured query behavior.

When would you use FastAPI TestClient versus an async HTTP client?

Chooses synchronous or asynchronous FastAPI test clients from the boundary exercised and resources involved.

FastAPIpytestPython

When would you use SQLAlchemy ORM, SQLAlchemy Core, or raw SQL?

Chooses a SQLAlchemy abstraction from the work's shape instead of performance slogans.

PythonSQLAlchemy

Architecture scenarioHard~15 min

Where should a SQLAlchemy transaction begin and end, and when are savepoints useful?

Aligns SQLAlchemy transactions with business operations and uses savepoints without inventing independent commits.

PythonSQLAlchemy

Architecture scenarioHard~15 min

Where should business logic live in a Django application?

Balances model methods, QuerySets, managers, and application services by the responsibility they own.

Architecture scenarioHard~10 min

Where should Python backend code catch, translate, or re-raise exceptions?

Places exception handling at meaningful boundaries and preserves causes, tracebacks, client contracts, and retry safety.

Debugging scenarioMedium~7 min

Why can mutable default arguments cause bugs in Python?

Diagnoses shared mutable function defaults and explains safe initialization without turning the behavior into a superstition.

Debugging scenarioHard~15 min

Why does a pytest monkeypatch sometimes have no effect, and where should you patch?

Explains Python name binding and patches the reference actually used by the system under test.

pytestPython

Architecture scenarioHard~15 min

Why does middleware order matter in Django?

Explains Django's nested middleware stack, short-circuiting, exceptions, and response unwinding.

Architecture scenarioHard~10 min

Why does middleware order matter in FastAPI and Starlette?

Explains nested ASGI middleware ordering, reverse response flow, exception boundaries, CORS, and streaming-safe design.

FastAPIPydanticPython

Concept questionHard~15 min

Why is deserializing untrusted pickle or unsafe YAML dangerous in Python?

Explains code execution during object reconstruction and chooses data-only formats with explicit validation.

Code reviewHard~15 min

Why must an Alembic autogenerated migration be reviewed before deployment?

Treats Alembic autogeneration as a candidate schema diff that still needs semantic and operational review.

AlembicPythonSQLAlchemy

Debugging scenarioHard~15 min

Why must Django data migrations use historical models?

Explains migration state, historical model lookup, replay safety, and the limits of migration-time models.