An ecommerce application runs behind an Application Load Balancer. A developer wants to analyze traffic patterns by client IP address to investigate unexpected load during off-peak hours. Which HTTP header should the developer inspect to get the originating client IP address?

The X-Forwarded-For header is a standard HTTP header that identifies the originating IP address of a client connecting to a web server through an HTTP proxy or load balancer. When an Application Load Balancer (ALB) receives a request, it adds or appends the client's IP address to this header before forwarding the request to the backend target. This allows the application to accurately log the client's IP for analytics, security, or debugging, even though the direct connection is from the ALB. X-Forwarded-Proto indicates the protocol (HTTP or HTTPS) the client used to connect to the load balancer. X-Forwarded-Host specifies the original host requested by the client. X-Forwarded-Port indicates the original port requested by the client. These headers provide other useful information but do not contain the client's IP address.