Vending Machine API

This project contains a number of hidden bugs. Your task is to debug and fix them. The goal is to solve as many as you can—it’s okay if you don’t find all of them.

Reference: The correct API behaviour is defined in api-specifications.md. Use it as the source of truth.

Workflow: Fork this repository and do all your work (and commits) in your fork.

Code quality: Read and understand the existing code and your own changes. Don’t apply fixes without understanding what the code does and why you’re changing it.

AI tools: You may use AI tools. If you do, you must share the relevant chat history with us during the interview.

Mandatory for the interview

• Bring your laptop.
• Ensure the project is set up on your machine before you come.
• If you used AI, have the chat history ready to share.

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FastAPI-based REST API for a vending machine system. See api-specifications.md for full specifications.

Setup

python -m venv .venv
source .venv/bin/activate   # or .venv\Scripts\activate on Windows
pip install -r requirements.txt

Configuration

Set environment variables (optional; defaults shown):

• MAX_SLOTS – maximum number of slots (default: 10)
• MAX_ITEMS_PER_SLOT – optional per-slot item limit
• DATABASE_URL – database URL (default: sqlite:///./vending.db)

Example:

export MAX_SLOTS=20

Run

uvicorn app.main:app --reload

API: http://127.0.0.1:8000
Docs: http://127.0.0.1:8000/docs

Endpoints

• POST /slots – create slot
• GET /slots – list slots
• GET /slots/full-view – slots with nested items
• DELETE /slots/{slot_id} – remove slot
• POST /slots/{slot_id}/items – add item to slot
• POST /slots/{slot_id}/items/bulk – bulk add items
• GET /slots/{slot_id}/items – list items in slot
• GET /items/{item_id} – get single item
• PATCH /items/{item_id}/price – update item price
• DELETE /slots/{slot_id}/items/{item_id} – remove item or quantity
• DELETE /slots/{slot_id}/items – clear slot or remove specific items
• POST /purchase – purchase item
• GET /purchase/change-breakdown?change=<amount> – change denomination breakdown
• GET /health – health check