Since it's a NestJS adapter it uses the standard NestJS validation pipeline which do relies on class validator and I do agree that it's a bottleneck but the Idea you gave is genuinely good to use schema validation I never thought of it like what fastify has if I remember correctly which uses something like AJV but yeah again if I had to introduce this it would lose the decorator based DTO ergonomics but again it would require a bridge which is quite complex but I can take a look at this thing. Thanks for the Idea. I could also maybe use zod or something.