Handling multiple event dependency in event-driven architecture : <p>What would be best practice if you have an event-driven architecture and a service subscribing to events has to wait for multiple event (of the same kind) before proceeding with creating the next event in the chain?</p>

<p>An example would be a book order handling service that has to wait for each book in the order to have been handled by the warehouse before creating the event that the order has been picked so that the shipping service (or something similar) picks up the order and starts preparing for shipping.</p>
