Query vs mutation vs subscription ing GraphQL?

Question

IT Interview Practice · Accepted Answer

Iku telu **operation type**, saben dipetakan menyang siji root type ing schema:

- **Query** — maca data. Field-e mlaku **sacara paralel** lan kudu tanpa efek samping (kaya HTTP GET).
- **Mutation** — nulis data (create/update/delete). Field tingkat ndhuwur mlaku **runtut**, mula urutane dijamin.
- **Subscription** — stream sing umure dawa: server ndudut data anyar menyang klien liwat transport kaya WebSocket saben ana event sing mletik.

```graphql
query GetPost {              # read
  post(id: "1") { title }
}

mutation AddComment {        # write; returns the created object so the client updates its cache
  addComment(postId: "1", text: "Nice!") {
    id
    text
  }
}

subscription OnComment {     # live: fires every time a comment is added
  commentAdded(postId: "1") {
    id
    text
  }
}
```

Mutation nampa **argumen** (kerep awujud object `input`) lan kudune **mbalekake data sing kena pengaruh** supaya klien bisa nyegerake tanpa request kaping pindho. Aturan runtut iku penting: rong mutation ing siji dokumen — `deposit` banjur `withdraw` — mesthi mlaku ing urutan kuwi, dene rong field query bisa uga diresolve bebarengan.

## Kenapa iki penting

Pewawancara ngecek apa kowe ngerti yen **query iku paralel lan tanpa efek samping dene mutation iku runtut**, lan yen subscription mbutuhake transport sing stateful (WebSocket/SSE). Mbalekake data sing wis diupdate saka mutation iku rincian praktis sing mbedakake wong sing wis tau ngirim GraphQL karo wong sing mung maca babagan iku.

Kenapa iki penting

Pitakon sing gegandhengan