Networking

Systems-level networking: sockets, async I/O, HTTP internals, and connection management.

Async I/O	epoll / kqueue / io_uring — how the OS notifies the runtime
TCP internals	Connection lifecycle, TIME_WAIT, keep-alive, Nagle's algorithm
HTTP/2	Multiplexing, flow control, header compression, stream priorities
Connection pools	Sizing, timeouts, health checks, circuit breaking