Clients receive HTTP 400 errors when calling an Amazon API Gateway endpoint. How can a developer investigate the cause of these 400 responses?

The correct approach is to enable execution logging and access logging for the API Gateway stage in CloudWatch Logs. Execution logs provide detailed information about requests, responses, and errors, including the full request and response bodies, which is crucial for diagnosing HTTP 400 errors. Access logs record who accessed your API and how, offering insights into client behavior. Supplying the ARN of a CloudWatch Logs log group ensures these logs are centrally stored and queryable. Incorrect options: Kinesis Data Firehose is for streaming data to various destinations, not directly for API Gateway logging. API Gateway integrates directly with CloudWatch Logs. CloudTrail Insights focuses on unusual API activity and security analysis, not detailed request/response debugging for individual API calls. AWS X-Ray is for distributed tracing and performance analysis, showing how requests flow through services, but it doesn't provide the detailed request/response payloads needed to debug HTTP 400 errors at the API Gateway level.