Go with fetch polyfill approach

next-js/src/app/gb-revalidate/route.ts

@@ -0,0 +1,10 @@
+import { NextRequest } from "next/server";
+import { revalidateTag } from "next/cache";
+
+// Use a route handler to refresh all cache entries related to GrowthBook.
+// GrowthBook SDK webhooks can be used to trigger this event immediately after
+// making a change on the platform.
+export const POST = (_req: NextRequest) => {
+  // TODO assert request is authorized from GrowthBook instance
+  revalidateTag("growthbook");
+};

next-js/src/app/server/combo/page.tsx

@@ -1,8 +1,6 @@
 import { createGB } from "@/lib/growthbook";
 import ClientComponent from "./ClientComponent";
 
-export const revalidate = 3600; // refresh cache every hour
-
 export default async function ServerCombo() {
   // create instance per request, server-side
   const gb = createGB();

next-js/src/lib/growthbook.ts

@@ -1,4 +1,20 @@
-import { GrowthBook, Context } from "@growthbook/growthbook";
+import { GrowthBook, Context, setPolyfills } from "@growthbook/growthbook";
+
+setPolyfills({
+  fetch: (
+    url: Parameters<typeof fetch>[0],
+    opts: Parameters<typeof fetch>[1]
+  ) =>
+    fetch(url, {
+      ...opts,
+      next: {
+        // cache results for an hour at most (static pages)
+        revalidate: 3600,
+        // see route handler for revalidating cache tagged under 'growthbook'
+        tags: ["growthbook"],
+      },
+    }),
+});
 
 // It's important to create a new instance per request when server-side to prevent
 // race condtions from occurring between different user requests.