Proxy, Reverse Proxy, and API Gateway¶
Modern distributed systems rely on intermediary networking components that sit between clients and servers. These components manage traffic, enforce security, and improve scalability.
The three most common architectural components are:
- Forward Proxy
- Reverse Proxy
- API Gateway
1. Forward Proxy (Proxy Server)¶
Definition¶
A Forward Proxy is an intermediary server that acts on behalf of the client when making requests to external resources on the internet.
Instead of communicating directly with a destination server, the client sends its request to the proxy, which then forwards the request to the target server and returns the response.
The destination server sees the proxy's IP address, not the client’s IP.
Common Use Cases
- Content Filtering
- Security Control
- Caching
- Logging and Monitoring
- Microservices (Sidecar Proxy)
In service mesh architectures, a proxy may sit next to a service to manage outgoing traffic.
Examples:
- Envoy
- Istio
Note
A forward proxy protects the client by hiding the user's identity from external servers.
2. Reverse Proxy¶
Definition¶
A Reverse Proxy sits in front of backend servers and handles incoming client requests, forwarding them to appropriate backend services.
Clients believe they are communicating directly with the server, but they are actually interacting with the reverse proxy.
Common Use Cases
- Load Balancing
- SSL/TLS Termination
- Caching
- Acts as security layer for backend server
Tip
Reverse proxies improve scalability, security, and performance of web infrastructure.
3. API Gateway¶
Definition¶
An API Gateway is a specialized reverse proxy designed specifically for managing APIs in microservices architectures.
It acts as the single entry point for all API requests from clients.
In microservices architectures, clients would otherwise need to communicate with multiple independent services, which introduces complexity.
An API Gateway simplifies this by:
- providing a single entry point
- managing cross-cutting concerns
Common Use Cases
- Routes incoming requests to the appropriate microservice.
- Authentication and Authorization
- Prevents abuse by limiting request frequency.
- Combines responses from multiple services into a single response.
- The gateway can translate between protocols.
- Provides centralized logging and metric
Note
API Gateways are most commonly used in microservices architectures.
4. Forward Proxy vs Reverse Proxy¶
| Feature | Forward Proxy | Reverse Proxy |
|---|---|---|
| Represents | Client | Server |
| Visibility | Server cannot see the real client | Client cannot see backend servers |
| Traffic Direction | Outbound traffic | Inbound traffic |
| Primary Goal | Privacy, filtering, caching | Load balancing, security, scalability |
5. Reverse Proxy vs API Gateway¶
| Feature | Reverse Proxy | API Gateway |
|---|---|---|
| Primary Role | Traffic management | API management |
| Scope | Web applications | Microservices APIs |
| Features | Load balancing, caching | Authentication, rate limiting, aggregation |
| Complexity | Lower | Higher |
6. Popular Implementations¶
| Technology | Category |
|---|---|
| NGINX | Reverse Proxy |
| HAProxy | Load Balancer / Reverse Proxy |
| Envoy | Service Mesh Proxy |
| Caddy | Reverse Proxy |
| Traefik | Cloud-native Reverse Proxy |
| Kong | API Gateway |
| AWS API Gateway | Managed API Gateway |