This is where the fractal nature of the role helps.
In your example, a mid level dev would oversee the architecture of the service. This dev would work to the junior to ensure their approach fits the rest of the service, and review their work. In turn a senior eng would oversee the architecture of the system owned by the team (possibly involving several services), and keep tabs with each one.
In your example, a mid level dev would oversee the architecture of the service. This dev would work to the junior to ensure their approach fits the rest of the service, and review their work. In turn a senior eng would oversee the architecture of the system owned by the team (possibly involving several services), and keep tabs with each one.
Delegation doesn't mean lack of accountability.