Explore the evolution of multi-threading applications and their impact on backend connection management in this comprehensive 50-minute episode of The Backend Engineering Show. Dive into five threading models, examining their pros and cons, and learn how they interleave with request handling. Begin with an introduction to single threading, then progress through multi-threading concepts, connection listeners, and the establishment of connections. Analyze various threading architectures, including single listener/worker thread, multiple worker threads, load balancing implementations, and the use of SO_REUSEPORT for multiple listeners on the same port. Conclude with insights on multiple single-threaded backend systems, gaining a thorough understanding of threads and connections in backend engineering.