I can mirror everyone singing praise to pocketbase here. Once you grasp the concepts (which map pretty closely to SQL concepts, with rules for row-based security), it is by far the easiest way IMO to create a maintainable, robust backend with direct auth integrations and a pleasant interface.

I have around 5 instances of pocketbase running on a 10 USD/month Hetzner server, serving thousands of users a day without breaking a sweat.