Logistics Microservice (Backend)

This is the backend service for the Logistics Application, built with FastAPI, PostgreSQL, and Docker. It handles inventory management, order processing, and strict concurrency control.

Prerequisites

• Docker Desktop (Must be installed and running)
• Git

Quick Start Commands

1. Start the Server

Run this command to build and start the database and API containers.

docker-compose up --build

The API will start on http://localhost:3000 check docker-compose.yml.

2. Apply Database Migrations

Once the server is running (in a new terminal), set up the database tables:

docker-compose exec web alembic upgrade head

3. Run Tests

To verify the application logic and locking mechanisms:

docker-compose exec web pytest

4. Stop the Server

To stop and remove the containers:

docker-compose down

API Documentation

Once running, you can access the interactive API docs here:

Swagger UI: http://localhost:3000/docs

Technical Design

Concurrency Handling: To prevent race conditions (overselling stock), this project uses Pessimistic Locking (SELECT ... FOR UPDATE) in SQLAlchemy. This ensures that when an order is being processed, the specific product row is locked until the transaction commits, preventing other parallel requests from modifying the stock simultaneously.

Frontend Repo Link

Repo of logistics-frontend: https://github.com/manojitht/logistics-frontend