How I wrote a Go message broker with a throughput of a million messages per second

I built HermitMQ entirely in Go. The main feature is ditching heavy wrappers like JSON in favor of a custom 29 byte binary protocol. Additionally, data transmission over the network uses a direct file to socket copy mechanism. I will go into detail about the architecture, data storage approaches, benchmark numbers, and show how it is implemented in code.

The full source code for the HermitMQ project is available on GitHub: https://github.com/ekhidirov/hermitmq

The problem with standard brokers and the cost of serialization

When the message counter exceeds hundreds of thousands per second, the main problem for a Go developer is the garbage collector. If every message is parsed via standard JSON, the application starts allocating a massive number of small objects in memory. The GC wakes up too frequently, eating up CPU time and causing network latency spikes.

To avoid triggering the garbage collector at every turn, I completely abandoned standard serialization libraries. Every message is packed into a custom header of exactly