How is the data accessed in marketing cloud custom activity?

Question

I'm a new developer in marketing cloud and I'm trying to develop a custom activity for journey builder. I would like to know if in an activity, the contacts are processed in batch mode or
each contact is processed alone ?

My goal is to make multiple callout to an external service from my custom activity but if the contacts in the DE are processed separately that would be a big problem.

Thank you

Answer 1

Contacts in Journey Builder are processed separately (1:1 communication: one contact, one API call).

If you want to send multiple contacts to an external webservice, you would need to develop a batching service on your server that you are trying to integrate with Journey Builder. There multiple HTTP posts sent from Journey Builder for each customer separately could be collected and sent in one API call to your external webservice.