How can I transition from a junior programmer to a senior developer without feeling overwhelmed by the responsibilities and expectations?

I completely understand your concerns, and it's great that you're thinking ahead. I've been in similar situations before, and I've found that the key is to start building those skills and taking on more responsibilities gradually. You don't want to take on too much too soon, but you also want to challenge yourself enough to prove your capabilities.

One thing that's worked for me is to focus on specific areas, like architecture, design patterns, and mentoring junior developers. These skills will not only make you a more well-rounded developer but also give you a chance to demonstrate your leadership capabilities. Start by reading up on these topics, and then try to apply them in your current projects. As you gain more confidence, you can start taking on more complex tasks and leading projects.

When it comes to demonstrating your capabilities to potential employers, I recommend working on projects that showcase your skills in those areas I mentioned earlier. For example, you could try refactoring a complex codebase to improve its architecture, or creating a design pattern library to share with your team. Share your projects on platforms like GitHub or GitLab, and don't be afraid to write about your thought process and the decisions you made. This will not only showcase your skills but also give you a chance to practice your communication skills.

Finally, don't forget to network and seek feedback from your colleagues and mentors. They can offer valuable advice and insights that will help you navigate the transition and make it a smooth one. Good luck, and I hope this helps!