So compromise. Take the current process model, add threading and shared memory, with feature flags to limit number of processes and number of threads. Want to

So compromise. Take the current process model, add threading and shared memory, with feature flags to limit number of processes and number of threads. Want to run an extension that isn't threadsafe? Run with 10 processes, 1 threads. Want to run high-performance? Run with 1 process, 10 threads. Afraid of "stability issues"? Run with 1 process, 1 thread. Will it be hard to do? Sure. Impossible? Not at all. Plan for it, give a very long runway, throw all your new features into the next major version branch, and tell people everything else is off the table for the next few years. If you're really sure threading is going to be increasingly necessary, better to start now than to wait until it's too late. But this idea of "oh it's hard", "oh it's dangerous", "too complicated", etc is bullshit. We've built fucking spaceships that visit other planets. We can make a database with threads that doesn't break. Otherwise we admit that basic software development using practices from the past 30 years is too much for us to figure out.