Stage 1 of 4: Search and filter the catalogue
Background. A library lending service: patrons borrow books, DVDs and magazines and place holds on items that are out. API.md is the contract every endpoint is held to. app.py routes requests to the handlers, and availability.py works out each item's status.
The catalogue page needs search and filters. Extend GET /api/items in items.py to support the search, itemType and status query parameters as API.md describes under Items. Seven tests in tests/test_part1_search.py fail.
Example
GET /api/items?search=harry&itemType=book&status=available →
[{"id": 1, "title": "Harry Potter and the Philosopher's Stone", "itemType": "book", "status": "available"}]
Done when Submit goes green.
Constraints
- Python 3.12+ standard library only
- Time limit: 5 seconds per test file
- Editable:
items.py,metrics.py,notifications.py - Read-only:
API.md,framework.py,store.py,models.py,auth.py,availability.py,loans.py,app.py,test_helpers.py, the public tests intests/
What comes after stage 1
The next stages open once the tests for the one before them pass. Each raises the bar, the way an interviewer does in the room.
- Stage 2: Fix the circulation panel.
- Stage 3: Tell holders their item is ready.
- Stage 4: Remind borrowers before and at the due time.
The files you get
- Yours to edit: items.py, metrics.py, notifications.py.
- Read-only: API.md, availability.py, loans.py, models.py, store.py, auth.py, framework.py, app.py, test_helpers.py, tests/__init__.py.
- Tests you can read and run: tests/test_part1_search.py. Hidden tests run on Submit.
The round: an agent in the editor
The assistant here works like the one in the interview IDE. It reads your files, runs code and proposes changes, and you accept or reject each one. It doesn't volunteer ideas, so what gets built is what you asked for. Along the way the interviewer asks about your decisions, and at the end the report says what you checked and what you accepted unread.
Frequently asked, briefly answered
Is Library Lending System: Search, Holds and Reminders free?
It is a Pro problem. Free plan includes one complete problem, plus the first stage of several more, so you can see how a round works before you pay.
Which company asks something like this?
Instacart. It is modelled on Instacart's round: Online "Full-Stack Engineer Assessment" on CodeSignal: 90 minutes, five connected sections on one library lending app (requirements from an AI product manager, a feature built with an in-editor Claude assistant, a bug fixed without it, then a larger notifications feature), scored by hidden tests.
Do I bring my own AI tool?
No. The assistant is in the editor, same as in the interview IDEs at Meta, Stripe and Amazon. What you choose at Begin is the format: an agent that proposes changes you accept or reject, an answer-only assistant that can't write code, or no assistant at all.
What does the interviewer ask?
4 questions along the way about your own code, and one at the end about the whole session. A weak answer gets one follow up. The answers go into the report, which ends with a hire or no hire verdict.
Start the problem
Sign in and the problem opens where you left it. New here? An account takes a minute to create, and the Pro plan starts at the first stage of this problem.
More like it: every practice problem, how Instacart runs its AI round, the AI coding interview guide.