Node.js Backend and Real-time App Development

I'm in need of a skilled Node.js engineer who can take on the tasks of building backend infrastructure and developing real-time applications. This is a medium-scale project, aimed towards serving several hundred users. The project is partway complete and the engineer will need to pick up where the previous developers left off, continue the development and bring it to completion. Professionals with prior experience in building scalable APIs, real-time applications and efficient backend infrastructure are preferred. Robust knowledge on working with existing code and improving upon it is a must.