There are a few things your developer should take into consideration when developing your site in terms of SEO.
The first is site load time. Not only is site load time a ranking factor in terms of search engines but a faster site is going to be better for your users and ultimately conversions. Your users aren’t likely to stay on a site that takes longer than a few seconds to load.
The next is having a mobile-friendly site. Mobile-friendly sites have started ranking higher in mobile searches so having a responsive or even a mobile-specific site is very important.