Hiring a JSTL developer can significantly improve the efficiency of your web application development process. JSTL, or JavaServer Pages Standard Tag Library, is a critical component of Java web development. A JSTL developer can leverage this standard tag library to separate the programming logic from the static HTML, promoting cleaner and more maintainable code. They can also streamline data processing, iteration, and condition checking, reducing the need for embedded Java code in HTML. In essence, a JSTL developer can enhance code readability, speed up development, and ultimately lead to the production of high-quality, robust web applications.