Python

Build a validated FastAPI create endpoint with safe models

Builds a FastAPI POST boundary with separate input/output models, forbidden extra fields, domain mapping, and a 201 response.

Can asyncio code have race conditions even when one event loop uses one thread?

Shows how task interleaving across await points can violate a multi-step invariant.

Does Django provide object-level permissions by default, and how should you enforce them?

Clarifies Django's object-permission hook and enforces ownership or tenancy in the query and policy path.

Does saving a Django model validate it?

Distinguishes Django model saving, explicit model validation, form validation, and database constraints.

Fetch URLs concurrently with a bound, timeout, and structured cleanup

Implements bounded asyncio HTTP concurrency with one client, per-call deadlines, TaskGroup ownership, and deterministic cleanup.

Fix a Django N+1 query and protect it with a query-count test

Repairs a Django serialization path with select_related and prefetch_related, then locks the query shape with a regression test.

Python Backend

Python backend interview preparation grounded in real service development.

A backend-focused Python preparation path covering language semantics, typing, FastAPI, Django, concurrency, data access, testing, security, background work, reliability, and production diagnosis.