# General Considerations

Keep these considerations in mind when using Pub/Sub API.

## AWS Regions

Pub/Sub API uses, for processing purposes, infrastructure that’s provided by Amazon Web Services, Inc. and located in the regions listed below.
By using the Pub/Sub API, you agree to the use of AWS infrastructure for processing purposes and acknowledge that such processing can occur outside the region where your production org is located. Event processing can cause data in transit to pass through and exist temporarily in an external region. If you use the Pub/Sub API endpoint specific to the region where your org is located, event processing occurs in the same region as your org. For more information, see [Pub/Sub API Endpoints](/docs/platform/pub-sub-api/guide/pub-sub-endpoints.md) and [Regions, Availability Zones, and Local Zones](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Concepts.RegionsAndAvailabilityZones.html) in the AWS documentation.

Regions:

- Asia Pacific (Mumbai, Sydney, Tokyo)
- Canada (Central)
- Europe (Frankfurt, London)
- South America (São Paulo)
- US East (N. Virginia)
- US West (Oregon)

Events in the Salesforce event bus aren't persisted or stored outside the region where your org is located.

## Channel Membership and User Permission Changes

If channel membership or user permissions change after a subscription starts and while it’s active, the changes take effect within 10 minutes. The same delay applies to publishing platform events. Here are some examples.

- If a new member is added to a channel, the client receives events corresponding to the new member within 10 minutes.
- If a user loses their View All permission on a Salesforce object included in a channel member, they stop receiving the object’s change events within 10 minutes.
- If a channel is deleted, the subscription ends with an error within 10 minutes. A channel can be a change data capture channel or a custom platform event channel.
- If a user loses their create permission for a platform event, they can’t publish the event anymore after 10 minutes or less.

For more information about change data capture channels and permissions, see [Subscription Channels](https://developer.salesforce.com/docs/atlas.en-us.change_data_capture.meta/change_data_capture/cdc_subscribe_channels.htm) and [Required Permissions for Change Events](https://developer.salesforce.com/docs/atlas.en-us.change_data_capture.meta/change_data_capture/cdc_security_perms.htm) in the *Change Data Capture Developer Guide*. For more information about custom platform event channels, see [Group Platform Events into One Stream with a Custom Channel](https://developer.salesforce.com/docs/atlas.en-us.platform_events.meta/platform_events/platform_events_subscribe_custom_channels.htm) in the *Platform Events Developer Guide*.

## Multiple Subscriptions and Duplicate Events

If you start multiple subscriptions for the same Salesforce org and topic, each subscription stream is independent of the others. The same events are delivered to each subscriber client. Add some logic in your client to handle duplicate events. The system-generated `id` field value in the received events uniquely identifies each event. You can dedupe events using the `id` field. If a Pub/Sub API publisher overrides the `id` field value, it's possible that the `id` isn't unique. See [Identify an Event with ProducerEvent.id and PublishResponse.correlationKey](https://review-app-sdevendoc-pr-88.herokuapp.com/docs/platform/pub-sub-api/references/methods/publishstream-rpc.html#identify-an-event-with-producereventid-and-publishresponsecorrelationkey). The `id` field corresponds to the `EventUuid` field in events delivered to non-Pub/Sub API clients. See [Identify and Match Event Messages with the EventUuid Field](https://developer.salesforce.com/docs/atlas.en-us.platform_events.meta/platform_events/platform_events_event_uuid.htm) in the *Platform Events Developer Guide*.

## IP Address Session Setting

The `Lock sessions to the IP address from which they originated` setting in the Session Settings page in Setup must be disabled for Pub/Sub API. If you enable this setting, Pub/Sub API RPC calls fail. For more information, see [Modify Session Security Settings](https://help.salesforce.com/s/articleView?id=xcloud.admin_sessions.htm\&type=5) in *Salesforce Help*.