remix-v2-perf-ssr

Remix v2 Performance, Streaming, Caching, Server/Client Split

Remix v2 has no built-in image optimizer and no opaque framework cache — it pushes everything to the standard HTTP layer. The performance surface is four pillars: streaming (defer/<Await>), HTTP caching (headers export), prefetching (<Link prefetch> and <PrefetchPageLinks>), and a hard server/client split (.server.* / .client.* file conventions).

Quick Reference

headers export with SWR (forward loader headers to the document):

import type { HeadersFunction, LoaderFunctionArgs } from "@remix-run/node";
import { json } from "@remix-run/node";

export async function loader({ params }: LoaderFunctionArgs) {
  const post = await cms.getPost(params.slug);
  return json(post, {
    headers: {
      "Cache-Control":
        "public, max-age=60, s-maxage=3600, stale-while-revalidate=86400",
    },
  });
}

export const headers: HeadersFunction = ({ loaderHeaders }) => ({
  "Cache-Control": loaderHeaders.get("Cache-Control") ?? "no-store",
});

.server.ts for server-only modules — build fails loud if the file leaks into the client graph:

// app/lib/db.server.ts — never bundled into the client
import { PrismaClient } from "@prisma/client";
export const db = new PrismaClient();

defer() for slow secondary data:

import { defer } from "@remix-run/node";
import { Await, useLoaderData } from "@remix-run/react";
import { Suspense } from "react";

export async function loader({ params }: LoaderFunctionArgs) {
  const product = await db.getProduct(params.id);   // critical, awaited
  const reviews = db.getReviews(params.id);          // slow, not awaited
  return defer({ product, reviews });
}

export default function Product() {
  const { product, reviews } = useLoaderData<typeof loader>();
  return (
    <>
      <ProductHeader product={product} />
      <Suspense fallback={<ReviewsSkeleton />}>
        <Await resolve={reviews} errorElement={<ReviewsError />}>
          {(r) => <ReviewList reviews={r} />}
        </Await>
      </Suspense>
    </>
  );
}