[UPDATED on 01/23/2018] Warning! It seems that Telegram X for Android turned out to be an unofficial client .
A month ago, Telegram released a special version of its iOS messenger called Telegram X. The application was completely written in the Swift programming language, created by Apple. Thanks to this, it worked several times faster. Today, the application officially came out for Android-devices.
Telegram X for Android is based on TDLib (Telegram Database Library) and is optimized for smartphones with 64-bit architecture. In addition, symmetric AES encryption has appeared for secure key exchange. Also there is an opportunity to choose the themes - Default Blue, Night Blue and Night Black, change the font size, enable automatic night mode and send files without limit in size.
Read in Russian: Теперь официальных клиентов Telegram под Android два: Telegram и Telegram X [ОБНОВЛЕНО]