Kepiye cara kerja revalidation on-demand (ISR)?

Question

Accepted Answer

**Revalidation on-demand** ngidini sampeyan invalidate kaca cached/static **persis kala data berubah** — tibatan ngenteni interval berbasis waktu. Iki minangka komplemen sing presisi kanggo ISR berbasis waktu (`revalidate: N`).

## Berbasis waktu vs on-demand

```tsx
// Time-based: page refreshes on a fixed schedule (may serve stale data up to N seconds)
export const revalidate = 3600; // every hour

// On-demand: refresh the INSTANT the underlying data changes — no waiting, no waste
```

ISR berbasis waktu simpel nanging ora sempurna: interval cekak = regenerasi sing ora perlu; interval dawa = konten ketinggalan. On-demand nggatasi iki kanthi trigger revalidation saka kode sampeyan kala ana owah-owahan.

## Rong API on-demand

```tsx
import { revalidatePath, revalidateTag } from "next/cache";

// 1. Tag your fetches, then invalidate by tag
await fetch("https://api/posts", { next: { tags: ["posts"] } });
revalidateTag("posts");      // refresh EVERY page/fetch tagged "posts"

// 2. Or invalidate a specific path
revalidatePath("/blog/my-post");
```

## Alur nyata: webhook CMS

```ts
// app/api/revalidate/route.ts — called by your CMS when an editor publishes
import { revalidateTag } from "next/cache";
import { NextRequest, NextResponse } from "next/server";

export async function POST(req: NextRequest) {
  const secret = req.nextUrl.searchParams.get("secret");
  if (secret !== process.env.REVALIDATE_SECRET) {       // verify it's really your CMS
    return NextResponse.json({ ok: false }, { status: 401 });
  }
  revalidateTag("posts");                                // rebuild affected pages now
  return NextResponse.json({ revalidated: true });
}
```

Alur: editor publikasi ing CMS → CMS nelpon webhook sampeyan → `revalidateTag("posts")` invalidate cache → pengunjung berikutne oleh HTML static sing regenerate. Kaca tetep static-cepet **lan** update langsung sak publikasi.

## Sawise mutasi Server Action

```tsx
"use server";
export async function createPost(data) {
  await db.post.create({ data });
  revalidateTag("posts"); // user sees their new post immediately
}
```

## Kenapa iki penting

Revalidation on-demand menehi sampeyan holy grail: **prestasi static kanthi kesegaran real-time**.

Sibatan ngira-ngira interval revalidation, sampeyan invalidate presisi kala konten berubah — liwat webhook (publikasi CMS) utawa sawise mutasi Server Action — nggunakake `revalidateTag`/`revalidatePath`.

Iki ngilangi konten ketinggalan lan regenerasi berlebihan sing mubazir, nggawekake ISR praktis kanggo konten sing update ora bisa diitung-itungi.