I’m 25 years old and have been working as a junior manager in a trading company for 4 years. Recently, our internal email said that another department is looking for a new boss. I sent my resume. But...

Thank you for sharing your situation. I understand why you feel disappointed; it can be discouraging when your capability is dismissed based on age... rather than performance. The fact that there are already managers in your company who are 26–27 shows that age alone shouldn’t be a barrier, so your reaction is completely valid.
It may help to reflect on two things:
(1) whether the company has a consistent, fair process for internal progression, and
(2) whether your skills and achievements are being meaningfully recognised.
There is no harm in having ambition at 25. In fact, your initiative to apply shows maturity. If your current environment undervalues young talent or fails to give you a clear pathway for growth, it’s reasonable to explore other companies that appreciate drive, competence, and potential.

At the same time, you could use this moment to request constructive feedback:
“What skills or experience should I build to be seriously considered for such roles in the near future?” A professional company should welcome that question. If their response remains dismissive or disrespectful, then your instinct may be right, it might be time to consider an environment where your contributions are respected. Ultimately, focus on where you can grow, be valued, and advance based on merit, not age. more