✳️ Our two cents about this:

➡️ Telegram never stores cloud chats in plaintext on the servers. They are encrypted.
➡️ Encryption keys are stored in a different facility in a different jurisdiction for each data center.
➡️ BUT if some intruder breach the security of all servers/facilities he will be able to access to your messages.
➡️ So Snowden is right about this: If you want full privacy, you should always use end-to-end encryption (keys are only stored on your device and never on telegram servers).

Fun fact: Long gone are the days when Pavel Durov offered Edward Snowden a job at Vkontakte.
http://money.cnn.com/2013/08/05/technology/social/snowden-vkontakte/