I have worked with a lot of people in a number of different companies (including a few startups) and I can think of a couple of engineers who really stood out.

I have worked with a lot of people in a number of different companies (including a few startups) and I can think of a couple of engineers who really stood out. When discussing engineering problems with these individuals, I never had to explain twice - Often, I didn't even need to finish my explanation and they already knew the optimal solution for that problem. These people are impressive to work with but I think it often comes down to experience more than intelligence (but they are usually very intelligent too). When an engineer has mastered a particular set of tools/languages/frameworks, they can come up with more optimal solutions and they can do it faster. A deep understanding of tools and techniques allows developers to look beyond the most obvious 'naive' solution to find the one which is the most suitable (using existing tools to do as much of the heavy lifting as possible). Also, when a developer cares deeply about a particular project, they will invest more time reading about relevant technologies in their own time. When it comes to learning new tools, most engineers are content to 'learn as they go' - That's OK, but it means that they are not as well equipped when it comes to finding that optimal solution. I think engineers should take time to familiarize themselves with tools REALLY WELL before they start using them, especially if such a tool/framework/technology will impact the project for many years in the future.