Originally published on software-engineer-blog.com.
You run code concurrently all the time. But "concurrent" hides a critical choice: are you spawning separate processes or threads inside the same process? That choice decides whether one crash takes down your entire system or stays contained, and whether you're copying data between isolated worlds or racing to read the same memory.
Mental model: A process is its own house; threads are roommates sharing one.
Processes: Isolation at the Cost of Weight
When you start a process, the operating system hands it its own private address space. That address space is walled off. Your process can't touch another process's memory—the OS enforces it at the CPU level. If your process crashes, it corrupts only its own memory. The kernel cleans it up. Every other process keeps running untouched.
