Discord's "stack"

Technologies Discord uses to provide the service, gathered from Discord's engineering articles and some other texts:

Storage:

Cassandra for storage
They used MongoDB as primary storage, but moved to Cassandra, source).
It is still unknown what role MongoDB has on the stack, but it is still a primary part of the service: source and source

Elixir for any real time communication, source.
Python for HTTP/REST API, The best guesses to which framework are Flask.
Go:
- The embed servers
- Punt
- Lilliput, which is a main part of their media proxy. Lillput is also written in C++. source!
Rust for many parts of the Discord Store, most commonly:
- Game SDK, to make Discord integrations for any game.
- Dispatch, which is a tool to send assets to Discord's servers.
C++ for the Discord RPC library.

Punt in favour of Logstash for logging.
Elasticsearch that powers the search feature for users and powers logging.
- Sources about logging: Punt and this issue
- Source about message search

Google's Cloud Platform for their infrastructure, source
Cloudflare as a proxy to almost all services, voice servers need to be direct connections, so they don't pass through CF.

WebRTC for voice and video. Source, which also goes on more detail on how the voice server architecture