Logic Apps Architecture

┌─────────────────────────────────────────────────────────────────────┐
│                    LOGIC APPS ARCHITECTURE                           │
├─────────────────────────────────────────────────────────────────────┤
│                                                                     │
│  TRIGGERS               ACTIONS               OUTPUTS               │
│  ┌──────────────┐      ┌──────────────┐     ┌──────────────┐     │
│  │ Recurrence   │─────>│ HTTP         │────>│ Email        │     │
│  │ HTTP Request │      │ Azure SQL    │     │ Teams        │     │
│  │ Event Grid  │      │ ADLS Gen2    │     │ Slack        │     │
│  │ Service Bus │      │ ADF          │     │ HTTP Response│     │
│  │ Blob Storage│      │ Databricks   │     │ Storage      │     │
│  └──────────────┘      │ Key Vault    │     └──────────────┘     │
│                         │ Logic Apps   │                          │
│  PLAN TYPES:             │ (Nested)    │                          │
│  ┌──────────────────┐   └──────────────┘                         │
│  │ Consumption:     │                                            │
│  │ Pay per action   │    CONNECTORS:                             │
│  │                  │    ┌─────────────────────────────────┐    │
│  │ Standard:        │    │ 300+ built-in connectors         │    │
│  │ Per app plan     │    │ • Azure services                  │    │
│  │ (dedicated)      │    │ • SaaS (Salesforce, SAP)         │    │
│  │                  │    │ • On-premises (via gateway)       │    │
│  └──────────────────┘    └─────────────────────────────────┘    │
└─────────────────────────────────────────────────────────────────────┘

Logic App Definition

{
  "definition": {
    "triggers": {
      "Recurrence": {
        "type": "Recurrence",
        "recurrence": {
          "frequency": "Hour",
          "interval": 1
        }
      }
    },
    "actions": {
      "Get_New_Files": {
        "type": "ApiConnection",
        "inputs": {
          "host": {
            "connection": {
              "name": "@parameters('$connections')['azureblob']['connectionId']"
            }
          },
          "method": "get",
          "path": "/v2/datasets/@{encodeURIComponent('raw')}/foldersV2/@{encodeURIComponent('incoming')}"
        }
      },
      "For_Each_File": {
        "type": "Foreach",
        "foreach": "@body('Get_New_Files')?['value']",
        "actions": {
          "Trigger_ADF_Pipeline": {
            "type": "ApiConnection",
            "inputs": {
              "host": {
                "connection": {
                  "name": "@parameters('$connections')['azuredatafactory']['connectionId']"
                }
              },
              "method": "post",
              "path": "/v1/subscriptions/@{encodeURIComponent('subscriptionId')}/resourceGroups/@{encodeURIComponent('resourceGroup')}/providers/Microsoft.DataFactory/factories/@{encodeURIComponent('factoryName')}/createRun",
              "body": {
                "referenceName": "pl_process_file",
                "parameters": {
                  "fileName": "@items('For_Each_File')?['name']"
                }
              }
            }
          }
        }
      },
      "Send_Alert": {
        "type": "ApiConnection",
        "inputs": {
          "host": {
            "connection": {
              "name": "@parameters('$connections')['office365']['connectionId']"
            }
          },
          "method": "post",
          "body": {
            "To": "data-team@company.com",
            "Subject": "Files Processed",
            "Body": "Successfully processed @{length(body('Get_New_Files')?['value'])} files"
          }
        }
      }
    }
  }
}

Key Vault Integration

# Logic App Key Vault connector
import requests
import json

# Secret rotation workflow
def rotate_secret(vault_name, secret_name):
    # Generate new secret value
    new_value = generate_secret_value()
    
    # Update Key Vault secret
    headers = {
        "Authorization": f"Bearer {get_token()}",
        "Content-Type": "application/json"
    }
    
    response = requests.put(
        f"https://{vault_name}.vault.azure.net/secrets/{secret_name}?api-version=7.4",
        headers=headers,
        json={"value": new_value}
    )
    
    return response.status_code == 200

Interview Questions

Q1: When would you use Logic Apps vs Azure Functions for data engineering? A: Logic Apps for workflow orchestration with many connectors (SaaS, Azure services). Azure Functions for custom code, complex computation, and event-driven processing.

Q2: How do you handle errors in Logic Apps? A: Use scopes with Try-Catch pattern, configure retry policies, implement error notifications, and use compensation actions for rollback scenarios.

Q3: What are the cost implications of Logic Apps? A: Consumption: ~$0.000025 per action. Standard: App Service plan costs. Use Standard for high-volume workflows; Consumption for sporadic workloads.