Can discuss estimate time further.
As a full stack developer with over 6 years of experience in web and software development, I believe I'm the right candidate to help you complete your website. Not only am I well-versed in the back-end technology you need, including Nest JS, but I also have solid knowledge and experience with databases and API integrations - all essential elements for building a platform like yours.
Throughout my career, I've successfully developed complex software applications using JavaScript frameworks like Angular, React, NodeJS(ExpressJS), and many more that might come up as enhancements for your website. Also, I've proficiently dived into databases you mentioned such as SQL (MySQL, PostgreSQL) and NoSQL (MongoDB, Mongoose). Moreover, having worked on APIs like Google Adwords or GoogleMap will be an added advantage for your site's integration needs.
One quality that sets me apart is my client-centric approach; I work until my client is happy. Keeping in mind the scale of the project similar to eBay and Amazon that you've mentioned, my experience and expertise will enable me to provide efficient solutions while adhering to tight deadlines. Let's connect and discuss further how I can contribute to your project. Thank you!