Blaqueyard

Personally I would have used Neo4j but am not sure if there's a library for nestjs. Another option I would have used mongodb.

Well for those performant tasks maybe you can use Rust nifs for elixir. Elixir enables to write fault-tolerant, scalable code for concurrent systems, and as such, it is perfect for messaging systems and web applications that might need to handle a lot of users efficiently. But if you need speed you can plug in Rust or write a microservice using Goland/Rust.