[recmend]

A good senior developer is proficient in more than one languages, knows or figures out quickly the pros and cons of any technology. They have both depth knowledge in certain part of the development stack and breadth overall.

Assessing seniority by just number of years of experience, or knowing a hot technology doesn't make one a senior developer. A solid Aptitude + Attitude towards software development will make you a stronger developer, and that will also help you pick up any new tools, needed to get the job done!

Good Luck!