Third option for me.

Communication is key, and minimising the reliance on another layer team to finish their bit or implement to the agreed interface correctly can greatly inhibit this.

I also prefer my team to be generalists who can easily move into different areas when needed. Got a new feature a "person" can work on he whole thing instead of waiting for 3 different people layers to all become available.

By all means have 1 DB expert keeping an eye on things there, and 1 UI expert monitoring that side of things, but having flexible multi talented people, working on feature silos rather than horizontal layers, for me, always works better.

Third option for me.

Communication is key, and minimising the reliance on another layer team to finish their bit or implement to the agreed interface correctly can greatly inhibit this.

I also prefer my team to be generalists who can easily move into different areas when needed. Got a new feature? A "person" can work on the whole thing instead of waiting for 3 different people layers to all become available.

By all means have 1 DB expert keeping an eye on things there, and 1 UI expert monitoring that side of things, but having flexible multi talented people, working on feature silos rather than horizontal layers, for me, always works better.