API keys for backend authentication create a fundamental challenge in web applications: the credentials need to authenticate requests but cannot be exposed to clients. Hardcoding keys in frontend bundles or environment variables leaves them visible in browser developer tools. Anyone who opens the network tab can extract the key and make unauthorized requests. Static configuration files require manual rotation and create operational risk—when a key needs to change, someone has to remember to update it everywhere.
This implementation solves these problems by injecting API keys at the edge using Cloudflare Workers and managing them centrally in AWS Secrets Manager with automatic rotation. The browser makes API requests without any authentication headers. The Cloudflare Worker intercepts these requests, adds the API key, and forwards them to the backend. The system rotates keys every 90 days, syncs them to Cloudflare automatically, and supports zero-downtime rotation through a dual-key architecture.