Querystring Value Missing

Question

API Gateway with custom domain mapped to Lambda function via Proxy integration. Noticed over the last few days that if a single querystring value is sent on a request (eg. domain.com?token=1234) then this is in the event object:

`"queryStringParameters": null,
"multiValueQueryStringParameters": null`

Yet if more than one is passed on a request (eg. domain.com?token=1234&t=1742471823) then this is in the event object:

`"queryStringParameters": {
        "t": "1742471823",
        "token": "1234"
    },
    "multiValueQueryStringParameters": {
        "t": [
            "1742471823"
        ],
        "token": [
            "1234"
        ]
    }`

Any ideas why this would have started happening? No changes have been made to the API Gateway or Lambda Function.

re:Post Agent · Answer

The behavior you're describing is unusual and not the expected functionality for API Gateway with Lambda proxy integration. Typically, both single and multiple query string parameters should be properly captured in the event object passed to the Lambda function.

Given that this issue started occurring recently without any changes made to the API Gateway or Lambda function, there are a few possibilities to consider:

1. Unintended configuration change: Although you mentioned no changes were made, it's worth double-checking the API Gateway configuration, especially the integration settings and any request/response mappings.

2. API Gateway service issue: There could be a temporary problem with the API Gateway service itself. AWS occasionally experiences service-specific issues that can affect behavior.

3. Caching issues: If you're using caching in API Gateway, it's possible that some cached responses are causing inconsistent behavior.

To troubleshoot this issue:

1. Verify the API Gateway configuration, ensuring that the proxy integration is set up correctly and there are no unexpected mappings or transformations.

2. Test with different combinations of query parameters to see if the problem is consistent across various scenarios.

3. If possible, try creating a new API with the same configuration to see if the issue persists in a fresh setup.

4. Check AWS service health dashboards and forums to see if other users are reporting similar issues.

5. If the problem continues, it may be worth contacting AWS support, as this behavior is not typical for API Gateway with Lambda proxy integration.

Remember, in a properly configured proxy integration, API Gateway should pass through all request data, including single and multiple query string parameters, without requiring additional configuration for individual parameters.  
**Sources**  
[HTTP API Gateway is only forwarding the first parameter string. | AWS re:Post](https://repost.aws/questions/QUeBoAMVqcSM2HW1UAlwtgsQ/http-api-gateway-is-only-forwarding-the-first-parameter-string)  
[API Gateway doesn't pass query parameters on to Lambda function when the resource is +proxy/ | AWS re:Post](https://repost.aws/questions/QUImXyL4bUSym-PZssCGunEA/api-gateway-doesn-t-pass-query-parameters-on-to-lambda-function-when-the-resource-is-proxy)

Querystring Value Missing

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