In order for other instances to discover your objects in a timely manner, you may want to push them. The recommended way to do this is to send the object directly to the push endpoint (listed in the remote instance's metadata), but for lightweight implementations you can also send just the URI of the object to the simplePush endpoint, which does not require any dynamic features on your end other than what's needed to look up the object.
It is highly recommended to impose a heavy delay and/or rate-limit on the simplePush endpoint to avoid it being abused (especially as it doesn't require a subscription).
Todo: expand on the following sections!
Rough process: first authenticate with the instance you want to push to, wait for them to subscribe to you, and then POST the entire object as JSON to their push endpoint.
Rough process: send a POST request to the simplePush endpoint, with the URI to the object you want to push as the request body (not form-encoded in any way).