Breakdown Metrics

Breakdown metrics help you visualize where your application is spending the majority of its time — allowing you to find the root cause of performance problems even quicker. These metrics are calculated for each transaction based on its corresponding types.

Page load breakdown

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Page load transactions breakdown aligns closely with the processsing model of the Navigation Timing API available in the browser. The different types of metrics are:

DNS - Duration of the DNS query for the current page (domainLookupEnd - domainLookupStart).
TCP - How long it took to establish the TCP connection to the server. Includes the TLS negotiation time for HTTPS pages (connectEnd - connectStart).
Request - The time elapsed between the browser making the HTTP request and receiving the first byte of the response (responseStart - requestStart). Also referred as TTFB (Time to First Byte).
Response - The elapsed time between the first and the last byte of the response. Referred commonly as Content Download time (responseEnd - responseStart).
Processing - Time taken to render the current page; this includes downloading necessary resources like JavaScript, Images, CSS, etc. required by the page (domComplete - domLoading).
Load - Duration of the load event after the browser is done dowloading the document and resources required for rendering the page (loadEventEnd - loadEventStart). Duration would be longer if there are multiple listeners for the load event.

Other transaction types

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For other transactions including SPA (Single Page Application) navigations and user created ones, the breakdown metrics are calculated based on the spans associated with the transaction.

If a SPA navigation transaction (route-change) spends 20% of the time downloading resources and 80% of the time waiting for the API call response, then the transaction breakdown would indicate time spent by span type as resource - 20% and http - 80%.
For a transaction that has concurrent async spans, the breakdown would include the sum of time spent by each span type.

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