Forward Proxy vs Reverse Proxy

Forward Proxy

Sits between client and internet. Client talks to proxy, proxy talks to internet on behalf of client.

Client --- Forward Proxy --- Internet
           (hides client)

Server sees proxy's IP, not client's IP — client identity is hidden.

Reverse Proxy

Sits between internet and servers. Client talks to proxy, proxy talks to backend servers on behalf of servers.

Client --- Reverse Proxy --- Backend Servers
           (hides servers)

Client sees proxy's IP, not server's IP — server identity is hidden.

Side by Side

Forward Proxy:
[Client] --- [Proxy] --- [Internet/Server]
 known      hides client    sees proxy

Reverse Proxy:
[Client] --- [Proxy] --- [Backend Servers]
 sees proxy   hides servers   known

Forward Proxy — Use Cases

Use Case	How
Bypass geo-restrictions	Client routes through proxy in another country
Corporate filtering	Company proxy blocks certain sites
Anonymity	Server never knows real client IP
Caching	Proxy caches responses for multiple clients

Examples: VPN, Squid proxy, browser proxy settings

Reverse Proxy — Use Cases

Use Case	How
Load balancing	Distribute traffic across servers
TLS termination	Handle HTTPS, pass HTTP to backend
Caching	Cache responses, reduce backend load
DDoS protection	Hide and protect origin servers
Rate limiting	Block abusive clients at proxy level
API Gateway	Route /api/users → user service, /api/orders → order service

Examples: Nginx, Cloudflare, AWS ALB, Traefik

Key Difference — Who Is Being Hidden?

	Forward Proxy	Reverse Proxy
Hides	Client	Server
Protects	Client's identity	Server's identity/infrastructure
Who configures it	Client side	Server side
Client knows about it	Yes	No

Nginx as Reverse Proxy (Common Interview Example)

Client --HTTPS--> Nginx (reverse proxy)
                     ├── Node.js app :3000
                     ├── Node.js app :3001
                     └── Node.js app :3002

Nginx handles TLS, load balancing, caching — backend just runs plain HTTP.