When new records are continuously added via API and you want to inject them into a journey, you should use Contact Evaluation set to Evaluate new records only. This ensures that only the newly added (not existing) records are evaluated for entry into the journey.

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Exact Extracts from Salesforce Documentation:

Source: Salesforce Help – Contact Evaluation Settings in Journey Builder

→ "When using a Data Extension Entry Source, you can choose to evaluate new records only, ensuring that only fresh entries are processed."

Source: Salesforce Help – Data Extension Entry Source

→ "Select 'Evaluate new records only' to inject new rows added to the data extension into the journey."

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