In 2014, Ericsson reported Erlang was being used in its support nodes, and in GPRS, 3G and LTE mobile networks worldwide and also by Nortel and T-Mobile.
Erlang is the programming language used to code WhatsApp.
Since being released as open source, Erlang has been spreading beyond telecoms, establishing itself in other vertical markets such as FinTech, gaming, healthcare, automotive, internet of things and blockchain. Apart from WhatsApp, there are other companies listed as Erlang's success stories: Vocalink (a MasterCard company), Goldman Sachs, Nintendo, AdRoll, Grindr, BT Mobile, Samsung, OpenX, and SITA.
A phone infrastructure programming language... for some reason
It's pretty widespread now, AWS is almost certainly using it alongside their RabbitMQ offering: https://aws.amazon.com/amazon-mq/
I guess it's very good at dispatching messages to lots of clients. It's always odd to me when large companies create new languages for their company when they are only superficially different or exist to enforce certain standards on their dev team.
In Erlang's case, they had a very specific set of requirements that weren't properly met by any existing languages. Lots of languages had individual qualities
they needed, but they couldn't find anything with all of them in one place.
Erlang reminds me of Ermac from Mortal Kombat.