Performance query concerning i18n translations


I am trying to find the best way to deal with translations for the text that appears in my application, e.g. form field labels, or blocks of text that are pre-defined. I notice that the majority of i18n packages, that can be used in a Meteor / React application, store the translations in json format a file. Do these packages get ALL of the string translations at once, say, when the the user logs in or when the application starts? Is there a performance hit by accessing ALL translations from a file, as opposed to say storing the translations in MongoDB and simply calling those that are needed either on a per page basis or a per component basis?