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API GatewayvsLoad Balancer
What is the difference between an API gateway and a load balancer?
Updated 2 min read6 differences
In short
A load balancer spreads traffic across copies of one service, while an API gateway is one front door that routes calls to the right service and checks auth.
API Gateway
An API gateway is a server that sits in front of a group of backend services and acts as the single entry point that receives, checks, and routes API requests.
Read the page on API GatewayLoad Balancer
A load balancer is a server or service that spreads incoming traffic across several backend servers so no single one is overloaded and the app stays available.
Read the page on Load BalancerAPI Gateway and Load Balancer compared
| Aspect | API Gateway | Load Balancer |
|---|---|---|
| The question it answers | Which service should take this call, and is it allowed? | Which copy of the server should take this request? |
| Routes by | Path, method, headers and API version | Server health and load |
| Works at | The HTTP level (L7), aware of APIs | The network level (L4) or the HTTP level (L7) |
| Extra features | Authentication, rate limiting, request rewriting, analytics | Health checks, TLS termination, sticky sessions |
| Typical scope | All the APIs of a system | One service with many instances |
| Examples | Kong, Amazon API Gateway, Apigee | NGINX, HAProxy, AWS Elastic Load Balancing |
The difference, explained
Both sit between clients and servers and pass requests along. A load balancer receives the traffic for one service and forwards each request or connection to one of several identical servers, using rules such as round robin or least connections, and stops sending traffic to servers that fail their health checks. An API gateway receives all the API calls for a system and decides, from the path, method or headers, which backend service should handle each one.
The difference is what they decide. A load balancer answers "which copy of this service?" and cares about capacity and availability. An API gateway answers "which service, and is this call allowed?": it can check API keys or tokens, apply rate limits, rewrite requests, combine responses and collect usage metrics, none of which a basic load balancer does.
They usually appear together. A typical setup puts a load balancer in front of several API gateway instances, and the gateway routes calls to services that are load-balanced in turn, often by Kubernetes or a service mesh. Some products blur the line: application load balancers can route by path, and many gateways can spread load across instances.
A common misconception is that an API gateway makes a load balancer unnecessary, or the other way round. Routing by path does not turn a load balancer into a full API management layer, and a gateway without redundancy and balancing in front of it becomes a single point of failure.
Which one should you use?
Choose API Gateway when…
- Clients call many microservices but should see one API.
- You want authentication, rate limits and usage tracking in one place.
- You need to version, rewrite or combine API requests.
Choose Load Balancer when…
- You run several copies of one service and want to share traffic between them.
- You need high availability, with unhealthy servers taken out of rotation automatically.
- The traffic is not only HTTP APIs, such as raw TCP connections.
Readers ask
Is an API gateway a load balancer?
Not exactly. Many gateways can spread traffic across instances, but their main job is routing and managing API calls; a load balancer's main job is distributing load.
Do I need both?
In larger systems, usually. A load balancer keeps the gateway itself available, and the gateway routes calls to services that are balanced on their own.
Is a reverse proxy the same thing?
Both are reverse proxies: they sit in front of servers and forward requests to them. Load balancers and API gateways are reverse proxies specialized in spreading load and in managing APIs.