Erlang is a functional programming language and runtime system designed for highly concurrent, fault-tolerant applications. Originally developed by Ericsson for telecom systems, it excels at building scalable and reliable networked applications. Many MQTT brokers, including EMQX and VerneMQ, are implemented in Erlang due to its stability under heavy loads. The language’s lightweight processes and “let it crash” philosophy make it ideal for distributed IoT systems. Erlang is less common in everyday development but plays a critical role in backend infrastructure. Its strengths directly contribute to the robustness of large-scale IoT platforms.