Webhook Receiver Flow
When Hubspot detects a change, it will send the data to the specified Flow as shown below.
The Receiver Block
Every Flow starts with a Receiver Block. Note the following things about this.
The Hubspot queue is specified. This ensures that Hubspot gets an immediate response. The actual Flow will be executed as jobs are processed form the Queue.
There is some Test Data supplied. This lets us test and debug our Flow without having to trigger a change in Hubspot each time.
Iterator
Hubspot can send many changes in one call, so the array might container many messages.
To deal with this, we use the Iterator Block (a Batching operation) to process one array element at a time. You'll note that the Batch End Block later in the Flow is responsible for looping back after each iteration.
Branch to Subflow
This evaluates an expression against the incoming data. It examines subscriptionId and executes a Subflow accordingly - each Hubspot webhook event has its own id.
Given the test data you can see in the Receiver Block subscriptionId: 3153733, this will execute the HSC Company Property Change Flow.
Batch End
Loops back to the Iterator Block until there is no more data left, after which the Flow will terminate.