AZURE LOAD BALANCER VS APPLICATION GATEWAY: KEY DIFFERENCES EXPLAINED

Azure Load Balancer vs Application Gateway: Key Differences Explained

Azure Load Balancer vs Application Gateway: Key Differences Explained

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When deploying applications in Microsoft Azure, ensuring high availability, scalability, and secure delivery of services is crucial. Two key services offered by Azure to distribute network traffic and improve application resilience are:





  • Azure Load Balancer




  • Azure Application Gateway




Though both serve the purpose of distributing incoming traffic across multiple backend resources, they cater to different use cases and operate at different layers of the OSI model.


In this guide, we’ll break down the differences between Azure Load Balancer and Azure Application Gateway to help you choose the right solution for your application architecture.






???? Azure Load Balancer Overview


Azure Load Balancer is a Layer 4 (Transport Layer) load balancer that distributes inbound traffic based on TCP/UDP protocols.



Key Features:




  • Operates at OSI Layer 4 (Transport Layer)




  • Supports TCP and UDP traffic




  • High-performance, low-latency traffic distribution




  • Provides internal (private) and public load balancing




  • Offers health probes to detect backend instance availability




  • Zone-redundant and highly available




  • Scales automatically to handle millions of flows




Use Cases:




  • Load balancing internet traffic to virtual machines (VMs)




  • Distributing traffic within virtual networks (internal load balancing)




  • High-throughput network applications




  • DNS, SQL, RDP, or other non-HTTP/HTTPS services







???? Azure Application Gateway Overview


Azure Application Gateway is a Layer 7 (Application Layer) load balancer and web traffic manager with advanced features designed for HTTP/HTTPS traffic.



Key Features:




  • Operates at OSI Layer 7 (Application Layer)




  • Provides URL-based routing, cookie-based affinity, and SSL termination




  • Integrated Web Application Firewall (WAF) for security




  • Supports end-to-end SSL encryption (SSL passthrough)




  • Custom routing rules based on URLs, headers, or query strings




  • Session persistence (sticky sessions)




Use Cases:




  • Hosting multiple web applications behind one IP




  • Securely serving HTTP/HTTPS content




  • Protecting apps from common web vulnerabilities using WAF




  • Routing traffic to microservices or containerized apps




  • URL path-based routing (e.g., /api → App1, /web → App2)







???? Azure Load Balancer vs Application Gateway: Feature Comparison










































































Feature Azure Load Balancer Azure Application Gateway
OSI Layer Layer 4 (Transport) Layer 7 (Application)
Protocol Support TCP, UDP HTTP, HTTPS, WebSocket
Use Case General purpose load balancing Web apps, HTTP(S) services
Routing Logic IP and port-based URL path, host headers, query strings
SSL Termination ❌ Not supported ✅ Supported
Web Application Firewall ❌ Not available ✅ Available (OWASP Core Ruleset)
Session Affinity (Sticky) Limited (via Source IP) ✅ Supported (cookie-based)
URL Path-Based Routing ❌ Not supported ✅ Supported
Autoscaling ✅ Built-in ✅ Built-in
Health Probes Basic TCP/HTTP Advanced health monitoring
Integration with App Gateway ❌ Separate Service ✅ Supports integration with Azure services
Pricing Lower cost, basic load balancing Higher cost, advanced features







???? When to Use Which?


Use Azure Load Balancer when:




  • You need fast, ultra-low latency network load balancing.




  • You’re working with non-HTTP protocols (e.g., RDP, SQL, FTP).




  • You require simple load balancing across VMs or services.




  • You’re building backend infrastructure without direct internet exposure.




Use Azure Application Gateway when:




  • You need advanced routing features like path-based routing or host headers.




  • You require application-level security with WAF.




  • You want to offload SSL processing (termination) for better performance.




  • You host multiple web applications on the same IP or domain.




  • You need to protect apps from OWASP top 10 threats.







???? Example Scenarios

































Scenario Best Choice
Load balancing HTTP/HTTPS traffic Application Gateway
Load balancing TCP-based backend services Load Balancer
Securing a web app with WAF Application Gateway
High-performance internal VM traffic routing Load Balancer (Internal)
Hosting multiple apps with URL-based routing Application Gateway







???? Security Considerations




  • Azure Load Balancer doesn’t inspect traffic content; it simply distributes it based on rules.




  • Application Gateway can decrypt, inspect, and re-encrypt traffic, making it ideal for environments where security and compliance are essential.







Conclusion


Choosing between Azure Load Balancer and Azure Application Gateway depends on your application’s specific needs. If you're dealing with general network-level traffic and need fast, efficient load distribution, go with Azure Load Balancer. However, if your application requires intelligent routing, web protection, or advanced traffic control features, then Azure Application Gateway is your best bet.


For many enterprise architectures, a combination of both services can also be used—for example, Load Balancer for backend services and Application Gateway for frontend web apps.


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