Secure Chat Site Backend Development

I need an experienced developer to build a secure backend for a chat site. The project should involve:

- Chat storage in MongoDB
- AES encryption for chat data
- Middleware development using your preferred framework (Express.js, Django, or Spring Boot)
- Implementing security measures to prevent SQL injection vulnerabilities
- Functionality for managing friends/contacts

Ideal skills and experience:
- Strong background in backend development
- Expertise in MongoDB and data encryption (AES)
- Familiarity with security best practices
- Experience in building middleware with one of the chosen frameworks

Please provide examples of similar work done.