rate limiting with @fastify/rate-limit

// server/index.ts
import fastify from 'fastify';
import fastifyRateLimit from '@fastify/rate-limit';
import { fastifyTRPCPlugin } from '@trpc/server/adapters/fastify';

import { appRouter } from './routers/index.js';
import { createContext } from './constants/context.js';

const server = fastify({ logger: { transport: { target: 'pino-pretty' } } });

// ...

await server.register(
  fastifyRateLimit,
  { global: false },
);

await server.register(
  fastifyTRPCPlugin,
  {
    prefix: '/trpc',
    trpcOptions: {
      createContext: createContext.bind(server),
      router: appRouter,
    },
  },
);

// ...

// server/routers/index.ts
import { inferRouterOutputs } from '@trpc/server';

import {
  middleware,
  procedure,
  router,
} from '../constants/trpc.js';
import rateLimited from '../middleware/rate-limited.js';

export const appRouter = router({
  demo: procedure
    .use(rateLimited({ max: 1 }))
    .query(() => null)
});

export type AppRouter = typeof appRouter;
export type RouterOutputs = inferRouterOutputs<AppRouter>;

// server/constants/trpc.ts
import { initTRPC } from '@trpc/server';

import type { Context } from './context';

const {
  middleware,
  procedure,
  router,
} = initTRPC.context<Context>().create();

export {
  middleware,
  procedure,
  router,
};

// server/constants/context.ts
import { CreateFastifyContextOptions } from '@trpc/server/adapters/fastify';
import { FastifyInstance } from 'fastify';

export function createContext(
  this: FastifyInstance,
  {
    req,
    res,
  }: CreateFastifyContextOptions,
) {
  return {
    app: this,
    req,
    res,
  };
};

export type Context = ReturnType<typeof createContext>;