[closeparen]

Here's a really simple way to get a cycle.

Service A: publish a notification indicating that some new data is available.

Service B: consume these notifications and call back to service A with queries for the changed data and perhaps surrounding context.

What would you recommend when something like this is desired?

[10000truths]

That's not a cycle - service B isn't writing any new data to A.

[9rx]

There is no cycle here.

Service B initiates the connection to Service A in order to receive notifications, and Service B initiates the connection to Service A to query for changed data.

Service A never initiates a connection with Service B. If Service B went offline, Service A would never notice.