The HTTP Server-Timing response header communicates one or more performance metrics about the request-response cycle to the user agent.
It is used to surface backend server timing metrics (for example, daTabase read/write, CPU time, file system access, etc.) in the developer tools in the user's browser or in the PerformanceServerTiming interface....Multiple metrics as a comma-separated list Server-Timing: <timing-metric>...Directives <timing-metric> A comma-separated list of one or more metrics...