I want to customized retry frequency of transaction so that 503 error can be prevented while pushing FHIR bundle to the LFS.

How do I achieve this?

Reference the following algorithm to increase the retry interval of IRIS transaction

An exponential backoff algorithm retries requests exponentially, increasing the waiting time between retries up to a maximum backoff time. The following algorithm implements truncated exponential backoff with jitter:

1. Send a request to the Cloud Healthcare API.
2. If the request fails, wait 1 + random-fraction seconds, then retry the request.