I guess OP did not explain one of the Fastify core features. On their website Schema based: even if it is not mandatory we recommend to use JSON Schema to validate your routes and serialize your outputs, internally Fastify compiles the schema in a highly performant function. It uses JSON Schema to do the run-time validation. That's different from TypeScript compile-time type-safety. JSON schema provides some basic abilities to do the validations, which might be good enough for most cases. By default Fastify uses Ajv to do the validation, but as the OP mentioned in another comment, you can switch to something else. Also, if you need to provide an OpenAPI/Swagger schema/documentation, there are also some plugins that can directly generate it from the Fastify end-points + JSON Schemas. The pain-points Fastify trying to resolve are, with JSON-schema-first approach, you simply write the JSON schema once, then you will get: solid validation with JSON schema on the end-points. with minimum work, like type IFooRequestParams = Static, you will get TypeScript types, which can be used in both back-end and front-end just to add a plugin, you will get OpenAPI schema. Of course only for end-points, you still have to write some general info of OpenAPI schema. With traditional back-ends, you have to manually validate API end-point parameters, write your OpenAPI schema separately, declare your types manually which easily go out-of-sync from your OpenAPI documentation. You do something once - JSON schema, and you will basically get other benefits for free: validation, OpenAPI schema, TS types for back-end, TS types reusable in front-end. If you don't need the validation and/or OpenAPI doc, it requires more work and sounds stupid. Actually, the whole point is JSON schema. There are a lot of resources built based on JSON schema. So you can write less code and get more benefits from the open-source community. btw, after did some research in the last month, I've totally bought what Fastify is selling. I will push Schema-Driven Development in my team soon. More on reddit.com

Why not use TypeBox which is officially supported? More on reddit.com

Thank you so much for this! I can see this indeed works, but this won't let me use type-checking with TypeScript, would it? I was simply referring to: https://fastify.dev/docs/latest/Reference/TypeScript/#typebox which shows the usage of generics: More on github.com

tsconfig-paths, tsc-alias, ts-node, nodemon, source-map-support and swc can all be replaced by tsx, using nodemon on a new project these days seems a bit like using something familiar especially since if you were keeping to JavaScript, node now natively watches for changes . Be mindful with using cross-env in a shared project, most of the time the job it does can be done with a .env file and means less dependencies, especially when it's not necessary on Linux / Mac / Windows with WSL2 or Windows with git bash. In your eslint config, I personally dislike airbnb because it includes stylistic actions but it's widely used so that's subjective, You didn't put the prettier config last which defeats its purpose. Also continuing the trend of opinionated stuff, using eslint-plugin-prettier can be considered by some to be very bad practice which you can read more about here and here Anyway, onto the main course. The code. First off, this doesn't look like Fastify, it looks like Nest.js ported to Fastify. You have used the logical OR (||) in a lot of places that ideally should be the Nullish coalescing operator ?? . You can ditch envalid too, you have Typebox and since you're using Fastify, you can use @fastify/env as well, that also lets you drop dotenv from your dependencies too. Try this instead import { Type, type Static } from '@sinclair/typebox import Fastify from 'fastify' import { TypeBoxTypeProvider } from '@fastify/type-provider-typebox' const app = Fastify().withTypeProvider() const schema = Type.Object({ NODE_ENV: Type.String() }); await app.register(fastifyEnv, { dotenv: true, schema }) declare module 'fastify' { interface FastifyInstance { config: Static } } declare global { namespace NodeJS { interface ProcessEnv extends Static {} } } Another thing you've done is pull in all the plugins to Fastify into one app.ts file and then load them in order, that works but you can chunk up your application if you embrace the Fastify encapsulated modules concept. Think Nest.js modules but in Fastify fashion. Move all your "services" to a modules folder, then in your app instantiating file include something like this to load every Fastify plugin in your module folder import { resolve, dirname } from 'node:path' import { fileURLToPath } from 'node:url' import Fastify from 'fastify' import fastifyAutoload from '@fastify/autoload' import { TypeBoxTypeProvider } from '@fastify/type-provider-typebox' const app = Fastify().withTypeProvider() await app.register(fastifyAutoload, { dir: resolve(dirname(fileURLToPath(import.meta.url)), 'modules') }) As for what the module files would look like? Well, something like this. import fp from 'fastify-plugin' import type { FastifyPluginAsyncTypebox } from '@fastify/type-provider-typebox' const prismaService: FastifyPluginAsyncTypebox = async (app) => { await app.decorate('prisma', new PrismaClient()) } export default fp(prismaService, { name: 'prismaService', /** This would be another module you make that just loads @fastify/env */ dependencies: 'env' }) declare module 'fastify' { interface FastifyInstance { prisma: PrismaClient } } I noticed in your initializeRoute.ts file, you had figured out the plugin pattern but had yet to find the built in types to make like easier. You want to use this instead: export const initializeRoutes: FastifyPluginCallbackTypebox<{ exampleOption: string }> = (server, options, done) => { ... } The HttpException class you created only exists to feel like nest.js in your service classes. You can ditch that and move your logic to the modules and with @fastify/sensible , you can quickly send errors using the decorated route handlers such as reply.notFound() Overall, it's a pretty neat project, I think you should check out this conference talk on how to structure a Fastify project if you're still excited for Fastify after my wall of text. edit: syntax corrections More on reddit.com