This is something that we've been encountering for a while but haven't found a fix for yet. We've implemented a site which may make multiple API calls, both using Shopify's built in API and our own external ones as well, however, we always encounter the Status Code 429: Too Many Requests when trying to create new customer accounts on our site.
We think that it's perhaps related to Ajax; when the submit button is called we use event.preventDefault() to handle the success in our own way. It works maybe once a day on each of our machines before trying to create further accounts results in the aforementioned 429, but I can't see how that alone is triggering multiple API calls resulting in too many requests. Does anyone have any idea why this is behaving like this?
Is there a way to get past this or to build a workaround? Any suggestions are thoroughly appreciated, thanks!