Building Production ETL Pipelines in Node.js with HazelJS Data

A comprehensive guide to the HazelJS Data Starter—decorator-based ETL, Schema validation, and data quality in TypeScript Introduction Data pipelines are the backbone of modern applications. Whether you're ingesting e-commerce orders, processing user profiles, or streaming events to analytics, you need reliable ETL (Extract, Transform, Load) with validation, quality checks, and a clean API. HazelJS is a decorator-first Node.js framework that provides @hazeljs/data —a module for pipeline orchestration, Schema validation, batch and stream processing, and data quality. In this post, we'll walk through the HazelJS Data Starter —a real-world example with order processing, user ingestion, and quality checks. Why ETL in Node.js? Node.js excels at I/O-bound workloads. ETL pipelines often involve: REST APIs receiving and responding to data Database reads/writes for persistence Stream processing for real-time events Validation before data enters your system Keeping ETL in the same runtime as your