Let’s shed some light on the API gateway vs load balancer debate. Each has a distinct purpose and use case, so let’s explore.
Understanding load balancers
Load balancers help you spread the load of your traffic in a way that supports efficient performance and easy scalability.
What is a load balancer?
A load balancer distributes traffic across multiple servers, balancing the load between them. Load balancer uses include supporting high availability and reducing the risk of bottlenecks.
How load balancers work
A load balancer sits between your backend and the client. It performs using algorithms. These dictate which of your servers the load balancer sends requests to.
Key features and capabilities
Load balancers support efficient content delivery, performance and speed. In addition to distributing traffic, they can monitor server health, reroute traffic in response to problems and reduce downtime, supporting uninterrupted operation and enhanced reliability via server failover.
Common load balancing algorithms
Some algorithms that load balancers commonly use include:
- Round robin – this static load balancing approach sends requests to servers in a pre-set order
- Weighted round robin – as above but with more requests sent to higher capacity servers
- Least connections – this dynamic load balancing approach targets requests at whichever server has the least number of active connections
- Weighted least connections – as above, but with more requests sent to higher capacity or higher bandwidth servers
- Least response time – this dynamic approach prioritizes servers with faster response times
- Least bandwidth – this sends requests to whichever server is handling the least requests
- Least packets – this prioritizes servers that have received fewer packets
- IP hash – this enables clients to connect with the same server for the duration of their session
Understanding API gateways
An API gateway allows for effective API management, security and analytics. It is a key component in the delivery of a streamlined, performant and secure API experience with fewer vulnerabilities.
What is an API gateway?
An API gateway is a single entry point for requests from clients to your backend. It makes securing and managing your APIs easier and can support API monetization, enabling you to get products to market faster, create new revenue streams and scale rapidly and efficiently.
Core functions of API gateways
API gateways handle a wide range of functions, including:
- Authentication and authorization
- Protocol mediation and transformations
- Routing
- Endpoint protection
- Caching
- Rate limiting/throttling
- Custom plugins and functions
- Analytics and tracing
- Logging
- Versioning
- Service discovery
- Circuit breaking
Is an API gateway a load balancer? No, but an API gateway can deliver load balancing. Tyk API Gateway, for example, supports native round-robin load balancing in its proxy.
Key features and capabilities
An API gateway ensures that only legitimate users access your services, defending against threats from unauthorized users. Its traffic management and caching capabilities support you to deliver reliable, performant services. As well as threats and vulnerabilities, the gateway defends against services being overwhelmed.
Through analytics, tracing and logging, API gateways also help with service health monitoring, efficient resource utilization and seamless compliance.
API gateway architecture
Similar to a load balancer, an API gateway sits between your backend and the client, though there is a difference between API gateway and load balancer positions within your stack.
Load balancer vs API gateway: The key differences
The main difference between a load balancer and an API gateway is their primary purpose. A load balancer distributes network traffic across multiple servers to optimize performance and ensure reliability.
An API gateway manages and routes API requests, adding features like authentication, rate limiting, and protocol translation to streamline interactions between clients and services.
Let’s take a look at this in more detail.
Request handling and routing
API gateway vs load balancer approaches to request handling and routing are markedly different. A load balancer uses algorithms to route requests. An API gateway uses pre-set rules and configurations for efficient content-based routing.
Security features
In terms of gateway vs load balancer security, load balancers can:
- Route traffic through firewalls
- Block malicious traffic
- Handle SSL termination, taking computational load off backend services
API gateways provide additional security services to mitigate threats, including:
- Authentication and authorization
- API keys and tokens
- Rate limiting
- Throttling
- Quota management
- Load balancing
- Circuit breakers
Some API gateways, such as Tyk, also provide custom plug-ins to suit specific security scenarios for your endpoints, as well as seamless integration with identity providers.
Performance management
Both a gateway and an API load balancer can help manage performance. A load balancer does this by distributing traffic between client and servers in a way that maximizes performance and reliability. It ensures no server is overloaded and reroutes traffic in the event of server failure.
An API gateway enhances performance through caching, reducing the load on backend services and making them less vulnerable to being overwhelmed. Monitoring and analytics capabilities support rapid error detection.
Scalability approaches
Load balancers support scalability through efficient resource utilization and preventing risky server overload situations. API gateways also support you to scale; you can scale the gateway to handle more concurrent requests.
Protocol support
Load balancers handle both network-level and transport-level protocols. Many deal with TCP and UDP, operating at layer 4 of the Open Systems Interconnection (OSI) model (transport layer). Others operate at layer 7 (application layer), routing traffic based on HTTPS headers, cookies or URL paths. Load balancers also operate at layer 3 (network) and layer 2 (data link).
API gateways operate at a higher level of abstraction. They can handle protocol translation, supporting simplified client-side experiences. The gateway can translate HTTP requests into WebSockets, gRPC or GraphQL requests, for example, so clients can use their preferred protocol to interact with your services.
When to use a load balancer
Choosing an API gateway vs load balancer depends on your use case.
Ideal use cases
Load balancers really come into their own in distributed systems and cloud environments. They can be effective for web services load balancing and as part of microservices architectures.
In addition to ensuring high availability and reliability, load balancers are ideal for:
- Failure handling
- Instance and server health checks
- Routing traffic based on specific situations/platforms (e.g. desktop versus mobile traffic)
- SSL termination
- Session persistence
- Preventing server overload
- Optimizing resource utilization
- Improving fault tolerance
- Scaling applications
- Data center load balancing
Benefits and advantages
These load balancer uses have many benefits. They include improved service reliability and uptime, as the load balancer prevents server overload and provides redundancy. This delivers heightened customer satisfaction.
Common implementation scenarios
Common load balancer implementation scenarios include:
- Web traffic distribution
- Cloud-based microservices
- Hybrid cloud load balancing
- Database load balancing
- Geographically distributed load balancing (global load balancing)
- Content delivery networks
- Scaling server farms
- Containerized applications (such as Kubernetes)
Limitations to consider
A load balancer’s primary purpose is traffic distribution, so it doesn’t inspect or manipulate data beyond its basic routing and balancing functions. Nor does it provide authentication, rate limiting or response transformations.
When to use an API gateway
If you’re seeking advanced application-layer functionality, such as authentication, rate limiting, request/response transformation and more, it’s time for an API gateway.
Ideal use cases
You can use an API gateway with microservices, Kubernetes, Ingress, service mesh and more. Modern gateways such as Tyk can handle all API protocols in a single platform, deployed across cloud, on-premise and hybrid environments.
Benefits and advantages
API gateway benefits include:
- Simplified API management
- Improved security
- Access control
- Support for robust API performance and reliability
- Graceful error handling and protection against cascading failures
- Reduced latency
- Seamless scaling
- Superior compliance journeys
Common implementation scenarios
Businesses implement API gateways for a wide range of reasons. With the gateway serving as a centralized entry point for client requests, some common implementation scenarios include using the gateway for:
- Authentication and authorization – within microservice-based and other architectures
- Data aggregation
- Securing API traffic
- Rate limiting and throttling (based on user, IP address, client and so on)
- Caching
- Versioning
- Request and response transformation
- Routing requests
- Load balancing
- Logging and monitoring
- SSL encryption/decryption
- Managing cross-origin resource sharing (CORS) policies
- Real-time event-driven API management
- Serverless API integration
- API monetization – through analytics, usage metrics and associated billing
- Implementing business logic mediation
- Edge service management
Limitations to consider
While API gateways suit a huge range of scenarios, they are not entirely without limitations. They introduce greater processing overhead than is usually seen with a load balancer, for example, both due to the layer at which they operate and as a result of performing complex logic on requests and responses.
Combining load balancers and API gateways
The question of API gateway vs load balancer isn’t an either/or one; you can use them together. Doing so means you enjoy the benefits of both.
Architecture patterns
Combining an API gateway with a load balancer in a traditional model means traffic will flow from the client to the gateway, then to the load balancer, and then to your servers. The gateway can also route traffic to services other than the load balancer, as required.
If your focus is on high availability and fault tolerance specifically, it’s also possible to sit the load balancer in front of the API gateway. The request then flows from the client to the load balancer, then through the gateway to the relevant backend service.
Other architecture patterns support different use cases, such as:
- A multi-region deployment for global applications
- A service mesh integration for decoupled and optimized environments with advanced traffic management
- A gateway as the sole entry point with a load balancer for internal microservice distribution
Benefits of using both
Using both an API gateway and a load balancer means you benefit from all the security, control and analytics that the gateway provides, along with the traffic management capabilities of the load balancer. The combination supports high availability, efficient resource utilization and robust security, also making it easy to maintain performance as you scale.
Implementation considerations
When implementing an API gateway with a load balancer, it’s important to consider how traffic will flow between them, how service discovery and auto-scaling will work, which will handle SSL termination and how health checks will support service resilience. Careful configuration is crucial.
Real-world examples
There are countless real-world examples of using API gateways and load balancers together, spanning all the architecture patterns above and more. You can even use a load balancer to check on the health of your gateway.
Making the right choice
API gateway vs load balancer: Which should you choose? Use these pointers to decide.
Decision framework
Bearing in mind the details above, consider your intended purpose/use case, whether you need security as well as traffic management, your scalability requirements and your likely future needs.
Cost considerations
API gateway pricing tends to center around request volumes, data processing or other usage metrics. Load balancer prices vary based on which layer they operate at, how much traffic they handle and number of rules. Be sure to shop around for both!
Performance impact
API gateways tend to have a greater performance impact than load balancers, as the gateway introduces higher latency. That said, there are multiple ways in which you can reduce the latency overhead of an API gateway, particularly through caching.
Implementation complexity
An API gateway offers more features and functionality than a load balancer, so is typically more complex to implement.
Best practices and tips
Keep the following in mind for your load balancer vs API gateway discussions.
Architecture design considerations
Use the gateway to handle cross-cutting concerns and consider multiple availability zones for the load balancer for high availability, fault tolerance and horizontal scaling.
Implementation guidelines
Choose your implementation strategy carefully, based on your security requirements and the nature of your traffic. Modular configurations and versioning can help for your APIs.
Common pitfalls to avoid
Avoid overloading your API gateway with excessive logic and too many calls. For dynamic scaling, don’t rely solely on DNS-based load balancing. And remember to avoid creating single points of failure.
Monitoring and maintenance
Use an API gateway to monitor usage patterns, latency and error rates and a load balancer for real-time health checks, with associated alerting for proactive maintenance.
Conclusion
You now have all the details you need to settle the API gateway vs load balancer debate. Go forth and implement!
Next steps
Elevate your strategy with these other API gateway articles in the Tyk Learning Center.
