Netlify

npm i -D @netlify/edge-functions

netlify/edge-functions/legacy-category-redirect.ts

import type { Config } from '@netlify/edge-functions';

const MAP: Record<string, string> = {
  '/hello-world': '/category/hello-world',
  '/sample-post': '/category/sample-post',
  
};

export default async (request: Request, context: { next: () => Promise<Response> }) => {
  const url = new URL(request.url);

  // /something/ -> /somethin
  const path = url.pathname.replace(/\/+$/, '') || '/';

  const target = MAP[path];
  if (!target) {
    return context.next();
  }

  url.pathname = target;

  return new Response(null, {
    status: 301,
    headers: {
      location: url.toString(),
      'x-legacy-redirect': '1', // debug
    },
  });
};

export const config = {
  path: [
    '/hello-world',
    '/sample-post',
  ],
};