Developer Builds NestJS Delivery Dispatch Backend with Concurrency Control and Dockerized Postgres

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A backend developer built a delivery dispatch service using NestJS, TypeORM, and PostgreSQL running in Docker containers to deepen their understanding of real-world backend engineering. The project goes beyond basic CRUD by tackling state transitions, route assignments, and data consistency under concurrent requests. To prevent duplicate route acceptances, the system uses concurrency guards that return an HTTP 409 Conflict error before any invalid state change reaches the database. The developer also wrote a Node.js automation script that resets the database schema by piping SQL queries directly into the Docker container, streamlining the testing process.

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