The best method is:
* Use an Engagement Split in Journey A to identify engagement.
* Use Update Contact Activity to update a Boolean field in a Data Extension based on the engagement result.
* Later, query this updated engagement Data Extension to inject subscribers into Journey B based on their behavior.
This avoids relying directly on querying system data views and enables near-real-time, easy-to-manage segmentation.
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Exact Extracts from Salesforce Documentation:
Source: Salesforce Help - Update Contact Activity in Journey Builder
# "Use Update Contact Activity to update attribute values for contacts during a journey based on behaviors such as engagement." Source: Salesforce Help - Journey Builder Engagement Split
# "Engagement Split evaluates engagement (open, click) and can trigger updates to data for further automation."
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