Building a Pub/Sub Broker from Scratch in Elixir Using Raw Process Primitives

Part 8 of a DEV Community series on distributed systems in Elixir focuses on building a Publish/Subscribe broker without relying on GenServer, Registry, or external libraries like Phoenix.PubSub. The tutorial explains why point-to-point messaging becomes problematic at scale, citing tight spatial and temporal coupling as key architectural drawbacks. A central broker is introduced as an intermediary that maintains a topic-based routing table, allowing publishers to broadcast events without knowing which subscribers are listening. The approach uses only Elixir's raw process primitives — spawn/1, send/2, receive/1, and Process.monitor/1 — to handle fan-out broadcasting and subscriber lifecycle management. The goal is to give developers a ground-level understanding of 1-to-many communication before adopting higher-level abstractions.