---
title: >-
  Improved concurrency handling in the Cart AJAX API and Storefront Cart GraphQL
  API - Shopify developer changelog
description: >-
  Shopify’s developer changelog documents all changes to Shopify’s platform.
  Find the latest news and learn about new platform opportunities.
source_url:
  html: >-
    https://shopify.dev/changelog/posts/improved-concurrency-handling-in-the-cart-ajax-api-and-storefront-cart-graphql-api
  md: >-
    https://shopify.dev/changelog/posts/improved-concurrency-handling-in-the-cart-ajax-api-and-storefront-cart-graphql-api.md
metadata:
  effectiveApiVersion: ''
  affectedApi:
    - displayName: Storefront API
      handle: storefront-graphql
  primaryTag:
    displayName: API
    handle: api
  secondaryTag:
    displayName: Update
    handle: update
  indicatesActionRequired: false
  createdAt: '2025-10-17T11:35:27-04:00'
  postedAt: '2025-10-21T18:00:00-04:00'
  updatedAt: '2025-10-22T09:21:49-04:00'
  effectiveAt: '2025-10-18T12:00:00-04:00'
---

October 21, 2025

# Improved concurrency handling in the Cart AJAX API and Storefront Cart GraphQL API

DateOctober 21, 2025

FlagsUpdate

SurfacesAPI

Affected APIs[Storefront API](https://shopify.dev/changelog?api_type=storefront-graphql)

As of October 10, 2025, the Cart AJAX API and Storefront Cart GQL API now processes simultaneous requests. For example, when sending two cart `add` requests at the same time, the Cart AJAX API executes both requests.

Previously, the Cart AJAX and GraphQL APIs were inconsistent in handling concurrent requests. This sometimes resulted in requests being dropped.

This is considered a bug fix for both APIs, but may require updates if the theme or storefront is unintentionally sending duplicate requests.

**Note**: If too many simultaneous requests are receieved, the Cart AJAX API will instead return an HTTP 409 response, while the Storefront Cart GraphQL API will return an error with code "CONFLICT" and message "Could not complete cart operation. The cart conflicted with another request".