Platforms and integrations are websites that need to do more. Rather than your typical brochure website, these are things like client portals, learning management systems or complete web applications.
My approach with these is always to start by building a Minimum Viable Product (MVP). This ensures that you're only paying for the features you need, rather than the full-featured application it will become.
By doing so, you can 'test the water' first, ensuring your monetization strategy works, and that you have a userbase for the platform, before fleshing out the additional features and functionality.
These projects are priced based on the brief and spec. With all my projects I invoice 50% to start, and 50% on completion.
Arrange a callWhen building platforms or integrating with APIs, I use NodeJS as a foundation, and tailor my stack around the requirements of the project.