refactor(infra): directory structure (#4615)

packages/backend/server/src/middleware/timing.ts

@@ -0,0 +1,27 @@
+import { NextFunction, Request, Response } from 'express';
+import onHeaders from 'on-headers';
+
+export const serverTimingAndCache = (
+  req: Request,
+  res: Response,
+  next: NextFunction
+) => {
+  req.res = res;
+  const now = process.hrtime();
+
+  onHeaders(res, () => {
+    const delta = process.hrtime(now);
+    const costInMilliseconds = (delta[0] + delta[1] / 1e9) * 1000;
+
+    const serverTiming = res.getHeader('Server-Timing') as string | undefined;
+    const serverTimingValue = `${
+      serverTiming ? `${serverTiming}, ` : ''
+    }total;dur=${costInMilliseconds}`;
+
+    res.setHeader('Server-Timing', serverTimingValue);
+  });
+
+  res.setHeader('Cache-Control', 'max-age=0, private, must-revalidate');
+
+  next();
+};