Learn how to add Input Validation to a REST API with NestJS and Prisma

A step-by-step guide on adding input validation and transformation to a NestJS REST API backed by Prisma and PostgreSQL. Covers setting up the built-in ValidationPipe globally, applying class-validator decorators to DTOs to enforce rules (min/max length, type checks), stripping unwanted properties via the whitelist option, and using ParseIntPipe to automatically convert string URL path parameters to integers. Also explains how NestJS pipes work and why decorator-based validation keeps controllers clean.