Kepiye carane nge-cache sawijining GraphQL API?

Question

IT Interview Practice · Accepted Answer

Nge-cache GraphQL luwih angel tinimbang REST amarga mung ana siji endpoint lan request biasane POST, mula caching HTTP basis URL ora langsung mlaku. Kanggo ngganti, kowe nge-cache ing telung lapisan: **klien**, **transport/CDN**, lan **server**.

## Cache klien sing dinormalisasi

Apollo Client lan Relay nyimpen asil ing **cache sing dinormalisasi** sing dikunci nganggo `__typename` + `id`. Saben object disimpen sepisan; query sing beda sing ngrujuk `User:1` sing padha bakal nganggo bareng, mula mutation sing ngupdate siji entitas nyegerake kabeh tampilan kanthi otomatis.

```graphql
# Both queries write to the same normalized entry User:1 in the client cache
query A { user(id: "1") { id name } }
query B { post(id: "9") { author { id name } } }  # author is also User:1
```

Kuwi sebabe field kudune mbalekake `id` — cache mbutuhake kunci sing stabil kanggo ndeduplikasi.

## Persisted query + CDN

**Persisted query** ngganti string query nganggo hash. Klien ngirim hash cendhak tinimbang badan POST sing dawa; server nggoleki query sing wis kadhaptar.

```js
// Automatic Persisted Queries: first a tiny GET with just the hash
// GET /graphql?extensions={"persistedQuery":{"sha256Hash":"abc..."}}
// -> because it's a GET with a stable key, a CDN can cache the RESPONSE at the edge
```

Ngowahi query maca dadi GET sing bisa di-cache ngidini **CDN** nyediakake ing edge, lan nyilikake payload. Petunjuk `@cacheControl` (max-age, scope) ngidini server ndeklarasi TTL per-field sing dihormati CDN lan cache server Apollo.

## Sisih server

Cache respons (contone duweke Apollo) sing dikunci nganggo query + variabel + scope auth ngindhari mbukak resolver maneh; DataLoader nangani deduplikasi per-request (urusan sing beda — iki dudu cache antar-request).

## Kenapa iki penting

Desain siji-endpoint/POST ngrusak caching HTTP sing naif, mula pewawancara pengin krungu jawaban sing **berlapis**: cache entitas sing dinormalisasi ing klien, persisted query + `@cacheControl` kanggo mbukak caching CDN/edge, lan ing ngendi DataLoader pas (per-request, dudu antar-request).

Cache klien sing dinormalisasi

Persisted query + CDN

Sisih server

Kenapa iki penting

Pitakon sing gegandhengan