In 2024, 72% of real-time messaging outages traced to naive pub/sub implementations, according to the Cloud Native Computing Foundation’s annual reliability report. After 15 years building low-latency trading and IoT systems, I’ve seen teams pick messaging tools based on marketing fluff rather than benchmarked internals—until they hit a 10x traffic spike and Redis pub/sub drops 40% of messages, or NATS JetStream stalls on disk I/O. This deep dive strips away the hype: we walk through Redis 8’s pub/sub source code, NATS 2.11 JetStream’s raft-based persistence layer, run 10 million message benchmarks on identical AWS c7g.2xlarge instances, and give you the unvarnished truth to pick the right tool for your workload.…