Solving 3 problems
Despite the evolution in #WebPerf with plenty of new timers and tools, there is still no definitive answer to some basic questions.
Not having a simple answer to those will maintain our challenges to influence why #PerfMatters.
Suppose you have performance measurements for 3 versions of a page:
Traditionally looking at the individual metrics Version 1 is the slowest and Version 3 is clearly the winner: The 3 tests share the same TTFB, Pageload and TTI, so we would focus on FCP and SpeedIndex. Version 3 has the fastest values for both FCP and SpeedIndex and following the mantra that faster is better must therefore have the better user experience.
Now is it? FRUSTRATIONindex claims Version 2 as the winner
Reason? Although further improving the FCP in Version 3 the increased gap between FCP and SpeedIndex leads to a bit more frustration.
FRUSTRATIONindex is NOT a timer, it is a score taking into account the gap between key timers. The longer a transition takes the bigger the frustration level for the user.