Duncan Brown posted a very interesting question on DZone: “Junior vs Senior Developers: What’s the Difference, Anyway?”
It occurred to me that the answer is, the ability to say “no.” No to additional feature requests, sacrificing personal life, unreasonable deadlines, etc. I’ve found that junior developers tend to be “yes” oriented (certainly I was) because, after all, one wants to eventually become distinguished as a senior developer. Enthusiasm is great and needed, but an over-enthusiastic “yes” can often lead the project, the team, and the company, into disaster when the repercussions of saying yes are encountered, often by the now, unhappy, customer.
A senior developer will say “no”, and even better (after some discussion on Code Project that led me to further clarity), will be able to explain why “no” is the appropriate answer, in such a way that management can make intelligent course corrections. Second, a senior developer will also say “no” and at the same time propose one or more alternatives for consideration. This facilitates out-of-the-box thinking that, again in my experience, often leads to better solutions that more easily achievable (meaning, less risk.)
Sure, there are lots of technical metrics one might use, but ultimately, I think the difference between junior and senior developers is reflected in their behavior when asked to accomplish something that is demonstrably unreasonable.