Change Data Capture Developer Guide

Change Data Capture
Keep Your External Data Current with Change Data Capture
Subscribe to Change Events
Change Event Message Structure
Security Considerations
Change Event Considerations
General Considerations
Change Event Allocations
Standard Object Notes
Sending Data Differences for Fields of Updated Records
Other Types of Change Events: Gap and Overflow Events
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Change Event Allocations

Concurrent Client Allocation

Description Performance and Unlimited Editions Enterprise Edition Developer Edition
Maximum number of concurrent CometD clients (subscribers) across all channels and for all event types 2,000 1,000 20

The concurrent client allocation is shared with all types of events that you can subscribe to through Streaming API, including PushTopic, generic, and platform events.

Note

Usage-Based Entitlements

Each Salesforce edition provides a default allocation for the number of change events delivered to CometD clients. The default allocation is enforced daily to ensure fair sharing of resources in the multitenant environment and to protect the service.

You can purchase an add-on license to increase your daily CometD event delivery allocation. This add-on license also removes the limit on the number of entities you can select for change notifications. With the add-on license, the CometD event delivery allocation depends on your monthly entitlement and scales with it. With the add-on, you can exceed the daily-equivalent allocation of the monthly entitlement by a certain amount for a 24-hour period. Event overages are calculated for a calendar month, starting with the first day of the month or your contract start date.

When you purchase an add-on license, the hourly event publishing allocation is increased by 25,000 events per month. To purchase more events, contact Salesforce.

The number of delivered events to external CometD clients is counted per subscribed client. If you have multiple client subscribers, your usage is added across all subscribers. For example, if you have an entitlement of three million monthly events, and one million events were delivered to two clients, you used up two million events, and you are still entitled to one million events for the month.

Table 1. Default Allocations
Description Performance and Unlimited Editions Enterprise Edition Developer Edition
Maximum number of delivered event notifications within a 24-hour period, shared by all CometD clients 50,000 25,000 10,000
Table 2. Example: Entitlement with One Add-On License for Three Million Events per Month
Description Performance and Unlimited Editions Enterprise Edition
Maximum number of delivered event notifications within a calendar month, shared by all CometD clients 4.5 million 3.75 million

The maximum event message size that you can publish is 1 MB.

Change events are based on platform events. If you receive both types of events, the usage-based entitlements of delivered change events and high-volume platform events are shared.

Note

Monitor Your Event Usage

To monitor your monthly event delivery usage, use the limits REST API resource and inspect the MonthlyPlatformEvents value. The limits resource returns the monthly maximum allocation. If you don’t have an add-on license, your daily default maximum allocation is the monthly allocation returned divided by 30. For more information, see List Organization Limits in the REST API Developer Guide.