Load Balancers Vs API Gateways
Great question — many developers confuse Load Balancers and API Gateways because they both sit in front of backend services. However, they serve different roles in an application architecture.
🧭 Quick Difference:
| Feature | Load Balancer | API Gateway |
|---|---|---|
| Purpose | Distributes traffic evenly to servers | Manages, routes, and controls APIs |
| Scope | Network-level traffic distribution | Application-level request management |
| Works With | Any kind of traffic (HTTP, TCP, etc.) | Primarily HTTP-based APIs |
| Intelligence | Simple routing (layer 4 or layer 7) | Smart routing with logic (auth, versioning) |
| Use Case | Balance load among multiple servers | Secure, monitor, and manage API calls |
🔀 Load Balancer
What it does:
- Distributes incoming traffic across multiple backend servers
- Ensures high availability and fault tolerance
- Works at Layer 4 (TCP) or Layer 7 (HTTP) of OSI model
Popular tools:
Nginx, HAProxy, AWS ELB/ALB, F5, Azure Load Balancer
Example:
🧩 API Gateway
What it does:
- Routes requests to specific services or endpoints
- Handles authentication, rate limiting, logging, transformations
- Supports microservices and versioning
Popular tools:
Kong, Amazon API Gateway, Apigee, NGINX (as API Gateway), Spring Cloud Gateway
Example:
🔧 Key Functional Differences:
| Functionality | Load Balancer | API Gateway |
|---|---|---|
| Load distribution | ✅ Yes | 🚫 Not primary function |
| Authentication | 🚫 No | ✅ Yes |
| Rate limiting | 🚫 No | ✅ Yes |
| SSL Termination | ✅ Yes (optional) | ✅ Yes |
| Routing by endpoint | 🚫 No (usually URL based only) | ✅ Yes |
| Protocol Support | TCP, HTTP(S), WebSocket | HTTP(S), WebSocket only |
✅ When to Use:
- Use a Load Balancer to:
- Distribute requests across multiple instances of the same service
- Ensure service uptime and fault tolerance
- Improve performance via parallelism
- Use an API Gateway to:
- Manage different microservices
- Apply centralized security policies
- Expose RESTful APIs or GraphQL APIs