Well the challenges faced by a web developer in an agency, company or a startup is roughly same except one fact that the learning curve goes up exponentially in a startup. • Development on new features - Working on new stuffs that are going to come up in future releases of your product. • Bugs - Fixing customer reported bugs. • Production Issues - It’s a startup, so there are competitors who are big giants maybe. Your product should be the best look-wise and equally importantly by performance. So working on production tweaks on the existing system to make sure your product is cutting edge fast and fully optimised. • Working with Complex Systems - There will be a dozens of different technologies that your startup might be using for development and definitely there will be different teams working on separate stuffs (for example UI/Backend/QA etc.) So you have to be really sure while fiddling with those code puppets so that your ‘strings’ don’t get tangled with something else.