How do I handle the pressure of making architecture decisions a whole team depends on?

You make the calls a whole team builds on, and you feel every year those choices will outlive. That weight is real. It also means you are taking the job seriously, which is why people trust you with it in the first place. But carry the weight honestly, not the fantasy of it. You are not deciding the next ten years. You are deciding the best next move with what you know today, in a system that will keep changing no matter what you pick. Good architecture is not the choice that is never wrong. It is the one that stays cheap to change when you learn more. Build for correction, not for perfection. When a decision starts to feel too heavy, write down what you are actually committing to and what you are leaving open. Name the parts that are hard to reverse and give those your real attention. Let the reversible parts stay light. You will carry less, and you will decide better.