You could become the "senior" person very quickly. Communicate clearly when things seem too vague or need domain knowledge that will take you time to properly i

You could become the "senior" person very quickly. Communicate clearly when things seem too vague or need domain knowledge that will take you time to properly investigate. Shortly after, make clear that you are doing more senior work now and that you expect the compensation to be readjusted. If things start looking too stressful, move to option 2 then 3.