Jira Cloud create object in Assets API returns 503 status code

I am trying to create objects in JSM Assets using Create Object API. When I call this API 70-80 times concurrently, it starts giving an error with a 503 status code. I am not getting any more information from headers such as Retry-After, etc. so I can determine the delay after which, I can start making more calls to this API again. I am using fetch to call this API from a Forge app.

Is there a bulk API to create objects in JSM Assets?
How can I handle such scenario to avoid 503 status code?