What is a proxy server?
Why Interviewers Ask This
This question tests conceptual clarity. Interviewers want to hear a precise, confident definition before moving to more complex Networking topics. It also reveals how well you can explain technical ideas to non-experts.
Answer
A proxy server is an intermediary server that sits between clients and destination servers, forwarding requests on behalf of clients. Forward proxy: used by clients to access the Internet — it hides the client's IP, enables caching (faster access to frequently visited sites), applies access controls, and can bypass geo-restrictions. Common in corporate networks to filter employee Internet access. Reverse proxy: sits in front of web servers, hiding their identities from clients. Used for load balancing (distributing traffic across multiple servers), SSL termination (offloading HTTPS from backend servers), caching, compression, and as a WAF (Web Application Firewall). Examples: Nginx, HAProxy, Cloudflare (reverse proxy/CDN). Transparent proxies intercept traffic without client configuration. Proxies operate at Layer 7 (Application layer), unlike NAT which works at Layer 3.
Pro Tip
Demonstrate both theoretical understanding and practical experience. Say what it is, then give an example of how you actually used it in a Networking codebase.