Blockchain is a less-touched technology, and the demand for expert developers is high. Before hiring blockchain programmers, you can consider their knowledge of blockchain technology. If the engineer is experienced and has worked on a similar project like yours, its a plus point. You can also check the testimonials from the previous clients they have worked for to know their strengths and weaknesses. The key is to know your project needs well and try to match them with the skills of the programmers.