What is Change Data Capture? | CRM Curator

Change Data Capture (CDC) is a built-in Salesforce feature that emits a streaming event every time a record is created, updated, deleted, or undeleted on the objects you enable. External systems subscribe to the event channel and stay in sync with Salesforce without polling and without anyone writing a trigger.

Why it exists

The traditional way to sync Salesforce data to an external warehouse:

Cron job runs every 15 minutes
Queries Account WHERE LastModifiedDate > :lastRun
Hopes nothing was deleted (deletes don’t show up in SOQL of the live table)
Pulls full record bodies, even if only one field changed
Burns API limits on every poll

CDC fixes all of that. The platform emits an event the moment a record changes. The event carries only the changed fields, plus the record Id, change type, and a header with replay metadata. Subscribers get notified in seconds.

What an event looks like

{
  "schema": "8FH...",
  "payload": {
    "ChangeEventHeader": {
      "entityName": "Account",
      "recordIds": ["001xx000003GeQqAAK"],
      "changeType": "UPDATE",
      "changeOrigin": "user/005xx000001SwiqAAC",
      "transactionKey": "0009b3...",
      "sequenceNumber": 1,
      "commitTimestamp": 1747497600000,
      "changedFields": ["Industry", "AnnualRevenue", "LastModifiedDate"]
    },
    "Industry": "Manufacturing",
    "AnnualRevenue": 5000000
  }
}

Notice: only the changed fields appear in the payload alongside the header. The subscriber doesn’t get a full record copy, just the delta.

How to enable it

Setup > Change Data Capture > Select Entities. Pick the objects you want streamed. Up to 5 custom + many standard objects on the free allocation; more requires CDC for All Objects licence.

Subscribers connect via:

Pub/Sub API (gRPC) — modern, recommended for any new build
CometD streaming API — legacy, still supported
Apex Trigger on the event channel — handle CDC inside Salesforce itself

Apex subscriber example

trigger AccountChangeTrigger on AccountChangeEvent (after insert) {
    for (AccountChangeEvent evt : Trigger.new) {
        EventBus.ChangeEventHeader header = evt.ChangeEventHeader;
        if (header.changeType == 'UPDATE'
            && header.changedFields.contains('Industry')) {
            // Re-rate territory, sync to data lake, etc.
        }
    }
}

CDC vs Platform Events vs PushTopic

Feature	CDC	Platform Event	PushTopic
Schema	Defined by the object	You define	SOQL query you write
Trigger	Any DML on enabled object	Explicit `EventBus.publish()`	Any DML matching the query
Use case	Data replication, sync	Custom business events	Legacy, mostly deprecated for new builds
Payload	Only changed fields	Whatever you put in	Full record snapshot

Limits

5 custom objects on standard allocation (more with add-on)
24-hour retention, 72-hour with High-Volume retention add-on
250,000 events per day shared with Platform Events
Replay by ReplayId for catching up after subscriber downtime

Common interview follow-ups

Use CDC or Platform Events for an order placed notification? — Platform Events. CDC is for syncing data state; Platform Events are for business signals.
Does CDC fire on bulk updates? — Yes, but events are grouped by transaction; you might receive one event per record or one event listing many recordIds (same transactionKey).
What about field-level security? — CDC ignores FLS — subscribers see all fields, so secure the subscriber side.

Verified against: Change Data Capture Developer Guide. Last reviewed 2026-05-17 for Spring ‘26 release.