X-Request-ID header can be used to trace individual requests to a web service (such as a REST API) from the client to the server and its backends.
A Client can send an HTTP header
X-Request-ID: some-value. The server should use the provided value and provide it in any requests that it makes to backend services for the purpose of serving the initial the request. When sending the response, the server will return the same header back to the client. For the purpose of tracing, the server will include the value into its logs, to enable correlating requests and responses with the corresponding logs.