https://api.kit.com/v4/bulk/.
In our bulk requests, we support synchronous processing for small batch sizes. The cut off size is clearly documented in each bulk request’s documentation below.
For large batch sizes, we use an asynchronous callback design. If you include a callback_url in your request body, we’ll POST to that URL when our processing has completed. Our POST request body will be the same response shape as our documented our synchronous 200 OK use case for each endpoint.
If you try to enqueue too many bulk requests at once, you’ll receive an error response with a 413 status code, which your code should gracefully handle. Try again after a short period.
We can recieve up to 300MB of request data per app, per creator account, before we respond with a
413 status. This is shared across all bulk requests (e.g. bulk creation of subscribers and tags).