Load Balancer vs Application Gateway decision in Azure - Performance Comparison

Time Complexity: Load Balancer vs Application Gateway decision

O(n)

Understanding Time Complexity

When deciding between Azure Load Balancer and Application Gateway, it helps to understand how their operations scale as traffic grows.

We want to know how the number of routing or processing steps changes when more requests come in.

Scenario Under Consideration

Analyze the time complexity of request handling by Load Balancer and Application Gateway.

// Simplified request handling
// Load Balancer forwards requests directly
// Application Gateway inspects and routes requests

foreach (var request in incomingRequests) {
  if (usingLoadBalancer) {
    ForwardRequest(request); // simple routing
  } else {
    InspectRequest(request); // deeper processing
    RouteRequest(request);
  }
}

This sequence shows how each request is processed differently by the two services.

Identify Repeating Operations

Each incoming request triggers operations:

• Primary operation: Forwarding or inspecting and routing a request.
• How many times: Once per request, repeated for every request.

The dominant operation is the per-request processing step, which differs in complexity between the two services.

How Execution Grows With Input

As the number of requests increases, the total processing steps increase roughly in direct proportion.

Input Size (n)	Approx. Api Calls/Operations
10	10 forwarding or inspection+routing operations
100	100 forwarding or inspection+routing operations
1000	1000 forwarding or inspection+routing operations

Pattern observation: The number of operations grows linearly with the number of requests.

Final Time Complexity

Time Complexity: O(n)

This means the processing time grows directly with the number of requests.

Common Mistake

[X] Wrong: "Application Gateway processes requests instantly regardless of volume."

[OK] Correct: Each request requires inspection and routing, so processing time adds up as requests increase.

Interview Connect

Understanding how request processing scales helps you explain design choices clearly and confidently in real-world cloud architecture discussions.

Self-Check

"What if the Application Gateway added caching to reduce inspection for repeated requests? How would the time complexity change?"