429 Too Many Requests When Adding Multiple Products Quickly to Cart – Is This Plan or Design Related?

Technical Q&A
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1

Hello Everyone,

We are facing an issue on one of our grocery Shopify stores where users add products to the cart very quickly (common behavior for grocery shopping). After adding around 10–20 products, the cart stops updating and products are not added successfully.

Upon investigation, we found that the Add to Cart JavaScript requests start returning an HTTP 429 – Too Many Requests error. After waiting for some time, the issue resolves automatically and users are again able to add products to the cart.

What we’ve observed:

  • Issue occurs when products are added rapidly

  • Cart API starts returning 429 rate limit errors

  • Issue resolves after a short cooldown period

  • No product or inventory-related errors found

Questions we’d like clarity on:

  1. Is this issue related to the Shopify plan (we are currently on the Shopify Basic plan)?

  2. Would upgrading the Shopify plan help mitigate or remove these rate limits?

  3. Is this behavior related to:

    • Internal Shopify cart API limits?

    • Store traffic levels?

    • Backend processes like discounts, scripts, or cart recalculations?

  4. Is this a theme / cart design issue, and should we redesign the Add to Cart logic to batch or throttle requests?

We would really appreciate guidance on best practices for handling high-frequency Add to Cart actions, especially for grocery or high-volume shopping use cases.

Looking forward to your insights and recommendations.

Thanks in advance!

2

Yes, Shopify does limit API calls rate.

Thought these are for Admin API, they can be used as guidelines.

Cart REST API does support adding multiple items to the cart in one call, so I’d rather do some consolidation before using API.