A.D.

Sometimes we want the front end of our blog to be translated for the users, but keep the backend admin panel in English. Admin in English with Switch does just that. It lets you switch your backend administration panel to English from admin toolbar, even if the rest of your blog is translated into another language. This plugin allows turning English language on and off for each user’s back-end independently.
For more information about original Admin in English plugin please visit https://wordpress.org/extend/plugins/admin-in-english/ page.

Admin in English with Switch

This plugin is an extended version of Admin in English plugin (v1.2) developed by Nikolay Bachiyski. See the Description for more details.

Sergey Biryukov

Converts gettext binary message catalogs to an array of strings. Allows to save some amount of RAM on a shared hosting server. 
Works with plugin and theme textdomains as well as with the default.
Thanks to AlexPTS for the idea.

Pure PHP Localization

Лучший и, скорее всего, единственный рабочий плагин. Спасибо, Сергей

Пожалуй, лучший плагин для кеширования переводов

Converts gettext binary message catalogs to an array of strings.

Admin in English with Switch vs Pure PHP Localization