Apa-apa lapisan caching sing ana ing Next.js?

Question

Accepted Answer

App Router duwe **sawetara lapisan caching** sing bekerja bebarengan. Ngerti babagan iki njelasake kenapa data kadhang kelihatan lawas lan carane ngontrol kesegaran.

## Patang cache

```text
1. Request Memoization — dedupes identical fetch() calls within ONE render pass
2. Data Cache          — persists fetch() results across requests & deploys (server)
3. Full Route Cache    — caches the rendered HTML/RSC of static routes (build time)
4. Router Cache        — client-side cache of visited routes (in the browser, per session)
```

## 1. Request Memoization

```tsx
// the SAME fetch in a layout AND a page → only ONE network request per render
const user = await fetch("/api/user"); // automatically deduped
```

## 2. Data Cache (sing paling sering disenengi)

```tsx
fetch(url, { cache: "force-cache" });       // cached (default) — like SSG
fetch(url, { cache: "no-store" });          // never cached — fresh every request
fetch(url, { next: { revalidate: 60 } });   // cached, refreshed every 60s — ISR
fetch(url, { next: { tags: ["posts"] } });  // taggable for on-demand invalidation
```

## 3 lan 4. Route cache

**Full Route Cache** menyimpan rute yang dirender secara statis; **Router Cache** menjaga rute yang sebelumnya dikunjungi di browser sehingga mundur/maju dan re-navigasi instant.

## Ngilangake cache saka mutasi

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

revalidatePath("/blog");        // invalidate a specific route's cache
revalidateTag("posts");         // invalidate every fetch tagged "posts"
router.refresh();               // (client) clear the Router Cache for current route
```

Sawise nggawe/ngedit data (asring ing Server Action), sampeyan manggile `revalidatePath`/`revalidateTag` supaya kaca-kaca sing kena daya metu maneh lan panganggone katon owah.

## Kesalahan umum

```text
"Why is my data stale after an update?" → a cache (usually Data or Router cache)
is serving the old value. Fix: revalidateTag/revalidatePath after the mutation,
or use cache: "no-store" for always-fresh data.
```

(Cathetan: default cache wis lumaku mengko ing rasi Next - tidho versi sampeyan, amarga sawetara versi anyar cache kurang agressif kanthi default.)

## Kepentingan

Caching multi-lapisan agresif Next.js iku sebabe cepet, nanging uga minangka #1 sumber kebingungan "kenapa data saya lawas?".

Ngerti patang lapisan, ngontrol Data Cache per-fetch (`no-store`/`revalidate`/tags), lan ngilangake karo `revalidatePath`/`revalidateTag` sawise mutasi penting kanggo entuk performance lan kesegaran sing bener.