430 Request Header Fields Too Large / Shopify Error
Meaning
A non-standard status code used by Shopify in two scenarios: earlier as a variant of 431 when too many URLs or headers were sent (deprecated in favor of 429/431), and also used to indicate a security or spam rejection by Shopify.
When to Use
Generally not used outside Shopify’s infrastructure. It was used when a client made too many rapid requests (instead of 429) or the headers were too large (instead of 431), or when Shopify detected a malicious request pattern.
Example
Older Shopify APIs might return 430 if a client exceeded certain request limits, or if a request was flagged as malicious or too large. For example, too many requests in a short time could yield 430 Shopify Security Rejection.
When Not to Use
Do not use in new implementations. Use 429 for rate limiting and 431 for header size issues. The 430 code is not part of any official HTTP standard and was specific to Shopify’s use cases.
Source
Unofficial (Shopify)