Server clock in epoch ms; public, unmetered. Use it to keep your nonce ahead.

Compare to your local Date.now() and offset your nonce by the difference.

A clock running fast is a one-way trap: the nonce it sends is stored, and once corrected every nonce you can produce is lower than the stored one, so the key 401s until an operator resets it. Checking here first is how you avoid needing that.