Reviewing a developer's portfolio and past projects can provide valuable insights into their experience and qualifications. Firstly, look for projects that are similar in nature or technology to your own. A developer with relevant experience is more likely to understand the challenges and requirements of your project. Pay attention to the scale and complexity of the projects they've worked on, as this can indicate their ability to handle projects of similar magnitude. Secondly, analyze the quality of their work by checking if the projects are functional, well-designed, and user-friendly. Consider the technologies they've utilized and their expertise in specific programming languages. For more tips, I suggest reading this article:
https://www.exposay.com/type-of-developer-is-right-for-project/