We'll close the chapter out with an overview of the performance implications introduced by the various configuration areas discussed thus far. If we really need configuration values in one area because they add value, they may hurt performance overall—so we need to offset this cost somehow.
By far the most noticeable performance bottleneck concerning locales is the initial load. That's because we have to load all the locale data before anything is actually rendered for the user. This includes string message translations, as well as all the other data necessary for localization. The performance during initialization is constrained further when there's more than one locale loaded up-front.
The best way to improve the load performance is to only load the locale that the user actually wants. Once they've set this preference, they're unlikely to change it frequently, so there's no real benefit to having other locale data nearby and ready.