Bulk SMS API Development

I'm looking for a professional to create an SMS API sender for me. This sender should primarily facilitate the sending of bulk messages. It will need to integrate seamlessly with a web application, and utilize API key for authentication.

Key Requirements:
- Proficiency in API development, particularly SMS API
- Experience with creating systems for bulk message sending
- Skills in integrating APIs with web applications
- Knowledge of implementing API key authentication

Please ensure your bid reflects your experience and capability to deliver a high-quality, fully functional SMS API sender.