Parallel http requests to google platforms with rate limit

From the design aspect, we like to have a backend connector that place parallel http requests to google drive platform

This platform has rate limit on the number of incoming requests per user.

Retry after header in the http response with status code 429 will help the connector to delay in invoking next http request, but this is synchronous behavior.

Using Retry after header, how do we achieve parallelism? By minimising number of 429 http responses that inturn improves responsiveness in front end

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Is there an industry proven algorithm that can allow parallel http requests with minimum 429 response?