How can I protect my API from DDoS attacks without paying for a service?

You can implement several measures independently: 1. Implement strict rate limiting on API endpoints. 2. Use CAPTCHAs or other challenges for suspicious traffic. 3. Configure robust firewalls and Intrusion Detection/Prevention Systems (IDPS). 4. Optimize your API and server for efficiency to handle more requests. 5. Use a Content Delivery Network (CDN) with basic DDoS mitigation features. 6. Monitor traffic patterns for anomalies and set up alerts.