A few things to look out for:
1. Error handling. In node you can't just wrap your code in a try/catch. And even if you register a listener for uncaught exceptions, you almost certainly have state shared between requests (for example, a database connection pool), which makes trying to handle such exceptions risky. To use node effectively, you need to be very careful to prevent exceptions from being thrown in unexpected locations.
2. Code rot. It is a lot less obvious what is idiomatic in Javascript as compared to Python, etc. Its easy to end up with a wide range of styles and patterns, which make maintenance difficult.
3. Missed or double callbacks. These are interesting mostly because they are not something you would see in synchronous code, and they can be quite difficult to troubleshoot (especially double callbacks).
Mitigating these issues is as much a cultural challenge as it is technical. Lint everything, review code aggressively, and don't merge code that doesn't have tests. Choose libraries carefully (the ecosystem has come a _long_ way in the last few years).
All of that being said, these are things you should be doing anyway. Develop a good tech culture, but get your product out and grow your user base. If you become the next Twitter you'll have the resources to undo any mistakes you make now.