Duplicate API Calls in Vibecoded Apps

Open the browser Network tab and filter by XHR/Fetch requests. Load a page and count how many times the same endpoint is called. If you see the same GET request firing two, three, or more times on a single page load, the app has duplicate fetch logic. This is extremely common when multiple components each fetch the same data independently.

Watch for duplicate POST requests when submitting forms. Click a submit button once and check if the Network tab shows one or multiple requests. Also monitor API calls during navigation — leaving and returning to a page should not re-fetch data that has not changed, especially if the data was fetched seconds ago.

Navigate to a data-heavy page and count the API requests in the Network tab. Then navigate away and come back — all the same requests fire again because there is no caching layer. Open multiple sections or tabs within the app that share data and watch the same endpoint get called for each one.

For duplicate mutation requests, click form submit buttons rapidly. Click a like or favorite button fast. Each click should be deduplicated or debounced, but AI-generated handlers typically fire independently for every click. Use the Network tab's throttling to slow requests and make the window for duplicate submissions larger.

Use a data-fetching library like React Query, SWR, or Apollo Client that provides automatic request deduplication, caching, and background refetching. These libraries ensure that multiple components requesting the same data result in a single API call.

For mutation requests, disable the submit button immediately on click and re-enable it only when the request completes or fails. Implement idempotency keys for critical operations so that duplicate requests on the server side are harmless. Add debouncing to search inputs and other fields that trigger API calls on every keystroke.