Apa iku change streams?

Question

Accepted Answer

**Change streams** ngidini aplikasi **subscribe menyang perubahan real-time** ing data MongoDB — nampa notifikasi nalika dokumen dimasukake, dianyari, utawa dihapus. Padha ngaktifake fitur reaktif, event-driven (update real-time, sinkronisasi, trigger) tanpa polling database. Dibangun ing replica set oplog.

## Nonton perubahan

```js
// watch a collection for changes — get notified in real time
const changeStream = db.collection("orders").watch();

changeStream.on("change", (change) => {
  console.log(change.operationType);   // "insert", "update", "delete", "replace"
  console.log(change.fullDocument);     // the changed document (for inserts/updates)
  // react: push to websockets, update a cache, trigger a workflow, etc.
});
```

Change stream ngeluarake event kanggo saben perubahan (insert/update/delete), kanthi rincian babagan apa sing owah — supaya aplikasi bisa ngreaksi kanthi real-time.

## Filter lan mulai maneh

```js
// watch only specific changes with an aggregation pipeline filter
db.collection("orders").watch([
  { $match: { operationType: "insert", "fullDocument.status": "urgent" } }
]);

// resume from where you left off (resilient to disconnections)
db.collection("orders").watch([], { resumeAfter: lastChangeToken });
```

Kowe bisa **filter** perubahan (nonton operasi utawa dokumen tartamtu) lan **resume** sawise putus (nganggo resume token) — nggawe change streams resilient.

## Use case umum

```text
✓ REAL-TIME features — push live updates to clients (websockets) when data changes
✓ SYNCING — keep a cache, search index (Elasticsearch), or another system in sync
✓ EVENT-DRIVEN architecture — trigger workflows/notifications on data changes
✓ AUDITING — log changes; analytics on data modifications
→ All WITHOUT polling the database repeatedly (efficient, real-time)
```

## Change streams versus polling

```text
❌ POLLING — repeatedly query "what changed?" → inefficient, latency, load on the DB
✅ CHANGE STREAMS — the database PUSHES changes to you in real time → efficient, instant
→ The right way to react to data changes (requires a replica set).
```

## Mulane penting

Change streams minangka fitur MongoDB sing berharga kanggo mbangun **aplikasi real-time, reaktif, event-driven**, mula mangerteni padha minangka pengetahuan tingkat senior sing berguna kanggo aplikasi modern sing butuh reaktivitas data langsung.

Nilai inti yaiku ngaktifake aplikasi kanggo **ngreaksi perubahan data kanthi real-time** — nampa push notification nalika dokumen dimasukake, dianyari, utawa dihapus — sing nggawa kapabilitas penting: **fitur real-time** (ngirim update langsung menyang klien liwat websocket nalika data owah — kebutuhan umum kanggo aplikasi kolaboratif, dashboard, notifikasi), **sinkronisasi** (njaga cache, search index kaya Elasticsearch, utawa sistem liya konsisten karo MongoDB nalika data owah), **arsitektur event-driven** (nggugah workflow, notifikasi, utawa processing nalika data owah), lan **auditing**.

Keuntungan kunci yaiku ngrampungake kabeh iki **tanpa polling** — change streams ngidini database *push* perubahan menyang aplikasi kanthi instan lan efisien, ngganti pola sing boros, latensi luwih dhuwur saka mbang-mbang query "apa sing owah?" (sing muatake database lan duwe penundaan).

Mangerteni cara nonton koleksi, filter perubahan (mung operasi/dokumen relevan), lan resume sawise putus (nganggo resume token kanggo resilience) nutupi panggunaan praktis.

Ngetok yen change streams butuh replica set uga relevan.

Sasab reaktivitas real-time lan njaga sistem tetep sinkron minangka kebutuhan aplikasi sing saya tambah penting, lan sasab change streams nyayake cara push-based sing efisien kanggo ngreaksi perubahan data MongoDB (luwih apik tinimbang polling), mangerteni change streams — apa sing nindakake, use case padha (fitur real-time, sinkronisasi, event-driven processing), kapabilitas resume/filter, lan keuntungan tinimbang polling — minangka pengetahuan tingkat senior sing berharga kanggo mbangun aplikasi MongoDB reaktif lan modern, fitur sing berguna kanggo kebutuhan umum tumuju ngreaksi perubahan data kanthi real-time lan topik sing nggambarake pamahaman babagan pola aplikasi event-driven lan real-time karo MongoDB.