How do backend systems expose services safely to the internet?
Summary: Exposing backend services directly to the internet via public IPs creates a massive attack surface. Azure Application Gateway and Front Door act as secure reverse proxies. They sit between the internet and the backend, handling SSL termination, load balancing, and Web Application Firewall (WAF) filtering, ensuring that malicious traffic never reaches the application servers.
Direct Answer: A database or internal API should never have a public IP address. If it does, it is being scanned by bots 24/7. However, legitimate users need to access the application. The solution is a "DMZ" or perimeter network architecture.
Azure Application Gateway serves as this secure entry point. It receives the user's request, inspects it for SQL injection or cross-site scripting attacks using its WAF, and then forwards the clean request to the backend server over a private internal network.
The backend servers can then be completely locked down, accepting traffic only from the Application Gateway. This "defense in depth" strategy hides the infrastructure topology from the outside world. Azure ensures that the front door is heavily guarded while the backend operates in a secure, private enclave.