Shopify has rolled out a significant update to its Cart AJAX API and Storefront Cart GraphQL API, improving how simultaneous requests are handled. This change, effective October 10, 2025, ensures that multiple cart operations are now processed sequentially, preventing dropped requests and offering a more reliable experience for merchants and their customers.
Key Takeaways
- Sequential Request Processing: Both the Cart AJAX API and Storefront Cart GraphQL API now process concurrent requests in the order they are received.
- Bug Fix Implementation: This update addresses previous inconsistencies in handling simultaneous requests, which could lead to dropped operations.
- Potential for Theme Updates: Merchants or developers whose themes or storefronts might be unintentionally sending duplicate requests may need to implement updates.
- Conflict Handling: In cases of excessive simultaneous requests, the Cart AJAX API will return an HTTP 409 response, while the Storefront Cart GraphQL API will issue a "CONFLICT" error.
Addressing Previous Inconsistencies
Prior to this update, the Cart AJAX API and the Storefront Cart GraphQL API exhibited inconsistent behavior when faced with multiple requests arriving at the same time. This inconsistency sometimes resulted in certain requests being unexpectedly dropped, leading to potential data loss or incomplete cart operations for users. This new sequential processing mechanism is a crucial bug fix, aiming to eliminate these issues.
Implications for Developers and Merchants
While this enhancement is designed to improve reliability, it's important for developers and merchants to be aware of the change. If a theme or storefront has been built with the assumption that duplicate requests might be ignored or handled in a specific, non-sequential manner, updates might be necessary. The goal is to ensure that all intended cart modifications are processed accurately.
New Conflict Response Mechanisms
Shopify has also clarified how the APIs will respond when an overwhelming number of simultaneous requests are received. For the Cart AJAX API, this will manifest as an HTTP 409 response, indicating a conflict. Similarly, the Storefront Cart GraphQL API will return an error with the code "CONFLICT" and a descriptive message: "Could not complete cart operation. The cart conflicted with another request." This provides clearer feedback when such situations arise, allowing for better error handling and debugging.
