Response Caching (v11)

Since all tRPC queries are normal HTTP GET requests, you can use standard HTTP cache headers to cache responses. This can make responses snappy, give your database a rest, and help scale your API.

Using `responseMeta` to cache responses

Most tRPC adapters support a responseMeta callback that lets you set HTTP headers (including cache headers) based on the procedures being called.

This works with any hosting provider that supports standard HTTP cache headers (e.g. Vercel, Cloudflare, AWS CloudFront).

server.ts

import { initTRPC } from '@trpc/server';
import { createHTTPServer } from '@trpc/server/adapters/standalone';
import type { CreateHTTPContextOptions } from '@trpc/server/adapters/standalone';

export const createContext = async (opts: CreateHTTPContextOptions) => {
  return {
    req: opts.req,
    res: opts.res,
  };
};

type Context = Awaited<ReturnType<typeof createContext>>;

export const t = initTRPC.context<Context>().create();

const waitFor = async (ms: number) =>
  new Promise((resolve) => setTimeout(resolve, ms));

export const appRouter = t.router({
  public: t.router({
    slowQueryCached: t.procedure.query(async (opts) => {
      await waitFor(5000); // wait for 5s

      return {
        lastUpdated: new Date().toJSON(),
      };
    }),
  }),
});

// Exporting `type AppRouter` only exposes types that can be used for inference
// https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-8.html#type-only-imports-and-export
export type AppRouter = typeof appRouter;

// export API handler
const server = createHTTPServer({
  router: appRouter,
  createContext,
  responseMeta(opts) {
    const { paths, errors, type } = opts;
    // assuming you have all your public routes with the keyword `public` in them
    const allPublic = paths && paths.every((path) => path.includes('public'));
    // checking that no procedures errored
    const allOk = errors.length === 0;
    // checking we're doing a query request
    const isQuery = type === 'query';

    if (allPublic && allOk && isQuery) {
      // cache request for 1 day + revalidate once every second
      const ONE_DAY_IN_SECONDS = 60 * 60 * 24;
      return {
        headers: new Headers([
          [
            'cache-control',
            `s-maxage=1, stale-while-revalidate=${ONE_DAY_IN_SECONDS}`,
          ],
        ]),
      };
    }
    return {};
  },
});

server.listen(3000);

Using responseMeta to cache responses

Using `responseMeta` to cache responses