Phil Calçado writes a detailed post on the non-technical side of why Soundcloud moved away from a monolithic Rails app, in favor of a microservices architecture. Main reason: productivity. They were able to reduce their time-to-launch of new features from 66 days to 16 days.
Originally published 2 years ago, Practicing Ruby provides a great explanation of what the Actor model looks like in Ruby. He solves the Dinning Philosophers Problem with bare ruby, the with Celluloid and then shows a simple implementation of actors in ruby would look like. Great read.
Did you know that when a process is forked in ruby, only the main thread is copied and all other threads are dead? Neither did I, until I ran into it recently. Solving threading issues is very hard. This post has great techniques on how to use threads in Rails, even if using forking servers.