Python Backend Interview Handbook: 160+ Real Questions with Runnable Answers: FastAPI, Async Python, SQL, and the Follow-Ups They Ask Next

Most Python interview books hand you a definition and wish you luck. Read the two-star reviews on the big ones and the same two complaints come up: too basic for anyone with real experience, and the code examples never show their output.

This book is built against both.

It follows one engineer, Neha Kulkarni, four years in, through one six-round interview loop at a payments company. Six rounds, six named interviewers, and 161 questions that land in the round where they would actually be asked. Every question gives you four things:

What it covers

Objects, references and mutability. Closures and decorators. The GIL, threads, processes, and what changed in Python 3.14 when free-threaded builds became officially supported. The standard 2019 answer to "can Python do parallelism" is now wrong, and interviewers have noticed. async/await and the single mistake that takes a FastAPI service down. FastAPI dependencies, lifespan and Pydantic v2. Django 6.0's async story and where django-ninja fits. Reading a query plan. Composite index column order. The N+1. SQLAlchemy 2.0 sessions and AsyncSession. Idempotency keys and the duplicate-charge bug. Caching, queues, retries, the outbox pattern. A scoped backend design round. Testing with pytest-asyncio, plus uv, ruff and mypy. The offer call, and negotiating level rather than money.

Who it is for

Engineers with roughly two to six years of Python who can do the job and have never had to narrate it. If most of those years were spent inside Django, chapters 2 through 5 are the ones to read twice.

Written against Python 3.14.7, FastAPI 0.141, Pydantic v2, SQLAlchemy 2.0 and Django 6.0. 269 pages. Includes a 48-hour plan for when the loop is on Thursday and it is now Tuesday night.

• The answer you say out loud, in one or two sentences
• The full explanation, starting from the problem the thing solves
• Code you can run, with its real output printed
• The two or three follow-ups that come next, which is where interviews are decided