[mrkeen]

If you write:

  int balance = 0;
  int get {...}
  void set(int balance) {...}
  void withdraw(int amt) {
    if amnt <= balance {
      balance -= amnt;
    }
  }

it will be flagged immediately in code review as a race condition and/or something that doesn't guarantee its implied balance>=0 invariant. Because threading.

But lift the logic up into a REST controller like pretty much all web app backends:

  GET /balance/get
  POST /balance/set
  POST /balance/withdraw

And it will sail straight through review. (Because we pretend each caller isn't its own Thread.)

[baggy_trough]

You're right, we can't get away from concurrency control with database, cache, even the file system. I'm still happy to never have to think about in-process multithreading bugs.