Enterprise Integration Architecture: EAI vs ESB vs API Gateway - Complete Guide 2025

Enterprise integration architecture requires choosing the right pattern for connecting systems, services, and applications. Enterprise Application Integration (EAI), Enterprise Service Bus (ESB), and API Gateway each serve different purposes and use cases. Understanding when to use each pattern and how to combine them is essential for building effective integration architectures.

This comprehensive guide covers enterprise integration architecture patterns, including EAI, ESB, and API Gateway approaches, when to use each pattern, hybrid architectures, and production deployment strategies. You'll learn how to design integration architectures, choose appropriate patterns, and implement production-ready solutions.

Integration Architecture Overview

Integration Challenges

Enterprise integration faces:

• Heterogeneous Systems: Different technologies and protocols
• Data Transformation: Format and structure differences
• Service Orchestration: Coordinating multiple services
• Protocol Mediation: Bridging different communication protocols
• Centralized Management: Single point of control

Integration Patterns

1. Enterprise Application Integration (EAI)

• Point-to-point connections
• Direct system integration
• Custom adapters
• Tight coupling

2. Enterprise Service Bus (ESB)

• Centralized message bus
• Service orchestration
• Protocol mediation
• Loose coupling

3. API Gateway

• Single entry point
• Request routing
• Authentication/authorization
• API management

Enterprise Application Integration (EAI)

EAI Characteristics

EAI provides:

• Direct Integration: Point-to-point connections
• Custom Adapters: System-specific connectors
• Data Transformation: Format conversion
• Business Logic: Integration workflows

EAI Implementation

Implement EAI with custom adapters:

public interface IIntegrationAdapter
{
    Task<IntegrationResult> SendAsync(object data);
    Task<object> ReceiveAsync();
}

public class SapAdapter : IIntegrationAdapter
{
    public async Task<IntegrationResult> SendAsync(object data)
    {
        // Transform to SAP format
        var sapMessage = TransformToSapFormat(data);
        
        // Send to SAP system
        await SendToSapAsync(sapMessage);
        
        return new IntegrationResult { Success = true };
    }
}

public class SalesforceAdapter : IIntegrationAdapter
{
    public async Task<IntegrationResult> SendAsync(object data)
    {
        // Transform to Salesforce format
        var salesforceMessage = TransformToSalesforceFormat(data);
        
        // Send to Salesforce
        await SendToSalesforceAsync(salesforceMessage);
        
        return new IntegrationResult { Success = true };
    }
}

When to Use EAI

Use EAI when:

• Few systems to integrate
• Direct connections acceptable
• Custom logic required
• Tight coupling acceptable

Enterprise Service Bus (ESB)

ESB Characteristics

ESB provides:

• Message Bus: Centralized messaging infrastructure
• Service Orchestration: Coordinate multiple services
• Protocol Mediation: Bridge different protocols
• Transformation: Message format conversion
• Routing: Intelligent message routing

ESB Implementation

Implement ESB with Azure Service Bus:

public class EnterpriseServiceBus
{
    private readonly ServiceBusClient _client;
    private readonly Dictionary<string, ServiceBusSender> _senders;
    private readonly Dictionary<string, ServiceBusProcessor> _processors;

    public async Task RouteMessageAsync(
        string messageType,
        object message)
    {
        // Transform message
        var transformedMessage = TransformMessage(message, messageType);
        
        // Route to appropriate destination
        var destination = DetermineDestination(messageType);
        
        if (_senders.TryGetValue(destination, out var sender))
        {
            await sender.SendMessageAsync(
                new ServiceBusMessage(JsonSerializer.Serialize(transformedMessage))
                {
                    Subject = messageType
                });
        }
    }

    public void RegisterProcessor(
        string queueName,
        Func<ServiceBusReceivedMessage, Task> handler)
    {
        var processor = _client.CreateProcessor(queueName);
        
        processor.ProcessMessageAsync += async args =>
        {
            await handler(args.Message);
            await args.CompleteMessageAsync(args.Message);
        };
        
        processor.StartProcessingAsync();
        _processors[queueName] = processor;
    }
}

When to Use ESB

Use ESB when:

• Many systems to integrate
• Complex routing required
• Service orchestration needed
• Protocol mediation required

API Gateway

API Gateway Characteristics

API Gateway provides:

• Single Entry Point: Unified API access
• Request Routing: Route to backend services
• Authentication: Centralized security
• Rate Limiting: Traffic control
• API Management: Versioning, documentation

API Gateway Implementation

Implement with YARP or Ocelot:

// YARP Configuration
builder.Services.AddReverseProxy()
    .LoadFromConfig(builder.Configuration.GetSection("ReverseProxy"));

var app = builder.Build();
app.MapReverseProxy();

{
  "ReverseProxy": {
    "Routes": {
      "orders-route": {
        "ClusterId": "orders-cluster",
        "Match": {
          "Path": "/api/orders/{**catch-all}"
        }
      }
    },
    "Clusters": {
      "orders-cluster": {
        "Destinations": {
          "destination1": {
            "Address": "https://orders-service:5001"
          }
        }
      }
    }
  }
}

When to Use API Gateway

Use API Gateway when:

• Public API exposure
• Multiple backend services
• Centralized security needed
• API versioning required

Hybrid Architectures

Combining Patterns

Use multiple patterns together:

public class HybridIntegrationArchitecture
{
    private readonly IApiGateway _apiGateway;
    private readonly IEnterpriseServiceBus _esb;
    private readonly Dictionary<string, IIntegrationAdapter> _adapters;

    public async Task ProcessRequestAsync(IntegrationRequest request)
    {
        // API Gateway for external requests
        if (request.Source == "External")
        {
            return await _apiGateway.ProcessAsync(request);
        }

        // ESB for internal service communication
        if (request.Source == "Internal")
        {
            return await _esb.RouteAsync(request);
        }

        // EAI for legacy system integration
        if (request.Source == "Legacy")
        {
            var adapter = _adapters[request.SystemType];
            return await adapter.ProcessAsync(request);
        }
    }
}

Architecture Layers

Layer integration patterns:

┌─────────────────┐
│  API Gateway    │  External API access
└────────┬────────┘
         │
┌────────▼────────┐
│  ESB            │  Service orchestration
└────────┬────────┘
         │
┌────────▼────────┐
│  EAI Adapters   │  Legacy system integration
└─────────────────┘

Choosing the Right Pattern

Decision Matrix

Requirement	EAI	ESB	API Gateway
Few systems	✅	❌	❌
Many systems	❌	✅	✅
Public API	❌	❌	✅
Legacy integration	✅	✅	❌
Service orchestration	❌	✅	❌
Protocol mediation	❌	✅	❌

Pattern Selection

Choose based on:

1. System Count: Few → EAI, Many → ESB/API Gateway
2. Integration Type: Legacy → EAI, Services → ESB, Public → API Gateway
3. Complexity: Simple → EAI, Complex → ESB
4. Coupling: Tight → EAI, Loose → ESB/API Gateway

Best Practices

1. Start Simple

• Begin with EAI for few systems
• Evolve to ESB as complexity grows
• Add API Gateway for public APIs

2. Use Hybrid Approach

• Combine patterns as needed
• API Gateway for external access
• ESB for internal orchestration
• EAI for legacy systems

3. Implement Proper Abstraction

public interface IIntegrationService
{
    Task<IntegrationResult> IntegrateAsync(IntegrationRequest request);
}

public class IntegrationService : IIntegrationService
{
    private readonly HybridIntegrationArchitecture _architecture;

    public async Task<IntegrationResult> IntegrateAsync(IntegrationRequest request)
    {
        // Abstract away pattern selection
        return await _architecture.ProcessRequestAsync(request);
    }
}

4. Monitor Integration

• Track message flows
• Monitor performance
• Alert on failures
• Measure throughput

5. Document Architecture

• Document pattern choices
• Maintain architecture diagrams
• Update as system evolves
• Share with team

Advanced Integration Patterns

Event-Driven Integration

Combine patterns with event-driven architecture:

public class EventDrivenIntegration
{
    private readonly IEventBus _eventBus;
    private readonly IApiGateway _apiGateway;
    private readonly IEnterpriseServiceBus _esb;

    public async Task ProcessIntegrationEventAsync(IntegrationEvent evt)
    {
        // Route based on event type
        switch (evt.Type)
        {
            case "ExternalApiRequest":
                await _apiGateway.ProcessAsync(evt);
                break;
            case "InternalServiceCall":
                await _esb.RouteAsync(evt);
                break;
            case "LegacySystemIntegration":
                await ProcessLegacyIntegrationAsync(evt);
                break;
        }
    }
}

Integration Patterns Comparison

Detailed comparison table:

Feature	EAI	ESB	API Gateway
Complexity	Low	High	Medium
Scalability	Limited	High	High
Protocol Support	Limited	Extensive	HTTP/REST
Service Discovery	No	Yes	Yes
Message Transformation	Basic	Advanced	Basic
Orchestration	No	Yes	No
API Management	No	No	Yes

Real-World Architecture Examples

Example 1: Hybrid EAI + ESB

Combine EAI adapters with ESB:

public class HybridEaiEsbArchitecture
{
    private readonly Dictionary<string, IIntegrationAdapter> _adapters;
    private readonly IEnterpriseServiceBus _esb;

    public async Task ProcessMessageAsync(IntegrationMessage message)
    {
        // Use EAI adapter for legacy system
        if (message.SourceSystem == "LegacyERP")
        {
            var adapter = _adapters["LegacyERP"];
            var transformed = await adapter.TransformAsync(message);
            
            // Route through ESB
            await _esb.RouteAsync(transformed);
        }
    }
}

Extended FAQ

Q: When should I migrate from EAI to ESB?

A: Migrate when:

• Integrating more than 5 systems
• Need service orchestration
• Require protocol mediation
• Need centralized management

Q: Can I use API Gateway with ESB?

A: Yes, common pattern:

• API Gateway for external access
• ESB for internal orchestration
• EAI adapters for legacy systems

Conclusion

Choosing the right integration architecture pattern depends on your specific requirements. By understanding EAI, ESB, and API Gateway patterns, and knowing when to use each or combine them, you can build effective enterprise integration architectures.

Key Takeaways:

1. Use EAI for simple integrations - Few systems, direct connections
2. Use ESB for complex orchestration - Many systems, service coordination
3. Use API Gateway for public APIs - External access, API management
4. Combine patterns - Hybrid approaches for complex scenarios
5. Start simple - Evolve architecture as needs grow
6. Monitor and document - Track performance and maintain documentation
7. Event-driven integration - Combine with event patterns
8. Evaluate requirements - Choose based on needs
9. Plan migration - Evolve architecture over time
10. Hybrid approaches - Best of all patterns

Next Steps:

1. Analyze integration requirements
2. Choose appropriate patterns
3. Design architecture
4. Implement integration layer
5. Monitor and optimize
6. Plan for evolution
7. Document decisions

Integration Architecture Best Practices

Implementation Checklist

• Analyze integration requirements
• Choose appropriate patterns (EAI/ESB/API Gateway)
• Design integration architecture
• Implement integration layer
• Set up monitoring and logging
• Test integration scenarios
• Document architecture decisions
• Review architecture regularly
• Optimize performance
• Plan for evolution

Production Deployment

Before deploying integration:

1. Test all integration patterns
2. Verify message routing
3. Test transformation logic
4. Validate error handling
5. Set up monitoring
6. Load test the system
7. Document procedures
8. Review security settings

Additional Resources

Integration Architecture Documentation

• Enterprise Application Integration
• Enterprise Service Bus patterns
• API Gateway patterns
• Integration best practices

Related Topics

• Message routing
• Protocol mediation
• Service orchestration
• Event-driven architecture

Integration Architecture Implementation Guide

Step-by-Step Setup

1. Analyze Requirements

   • Identify systems to integrate
   • Determine integration patterns
   • Assess complexity
   • Plan architecture

2. Choose Patterns

   • EAI for simple integrations
   • ESB for complex orchestration
   • API Gateway for public APIs
   • Hybrid for complex scenarios

3. Design Architecture

   • Design integration layer
   • Plan message routing
   • Design transformation logic
   • Plan error handling

4. Implement Integration

   • Build integration components
   • Implement message routing
   • Create transformations
   • Add error handling

5. Deploy and Monitor

   • Deploy integration layer
   • Set up monitoring
   • Test integration flows
   • Optimize performance

Integration Patterns

EAI Adapter

Create EAI adapter:

public class LegacySystemAdapter
{
    public async Task<IntegrationMessage> TransformAsync(LegacyMessage legacy)
    {
        return new IntegrationMessage
        {
            Id = legacy.RecordId,
            Type = "Shipment",
            Data = TransformLegacyData(legacy)
        };
    }
}

ESB Router

Create ESB message router:

public class MessageRouter
{
    public async Task RouteMessageAsync(IntegrationMessage message)
    {
        var route = DetermineRoute(message);
        
        switch (route.Destination)
        {
            case "OrderService":
                await SendToOrderServiceAsync(message);
                break;
            case "InventoryService":
                await SendToInventoryServiceAsync(message);
                break;
        }
    }
}

Integration Architecture Advanced Patterns

Message Orchestration

Orchestrate multiple services:

public class ServiceOrchestrator
{
    public async Task<OrchestrationResult> OrchestrateAsync(
        OrchestrationRequest request)
    {
        var results = new List<ServiceResult>();

        // Step 1: Validate
        var validation = await ValidateRequestAsync(request);
        results.Add(validation);

        // Step 2: Process payment
        var payment = await ProcessPaymentAsync(request);
        results.Add(payment);

        // Step 3: Reserve inventory
        var inventory = await ReserveInventoryAsync(request);
        results.Add(inventory);

        // Step 4: Fulfill order
        var fulfillment = await FulfillOrderAsync(request);
        results.Add(fulfillment);

        return new OrchestrationResult
        {
            Success = results.All(r => r.Success),
            Results = results
        };
    }
}

Protocol Mediation

Mediate between different protocols:

public class ProtocolMediator
{
    public async Task<MediatedMessage> MediateAsync(
        IncomingMessage incoming, 
        string targetProtocol)
    {
        // Convert to internal format
        var internal = await ConvertToInternalFormatAsync(incoming);
        
        // Transform for target protocol
        var transformed = await TransformForProtocolAsync(internal, targetProtocol);
        
        // Send to target
        return await SendToTargetAsync(transformed, targetProtocol);
    }
}

Integration Architecture Patterns

EAI Pattern Implementation

Implement EAI pattern:

public class EAIIntegration
{
    public async Task<IntegrationResult> IntegrateAsync(
        SourceSystem source, 
        TargetSystem target)
    {
        // Extract data from source
        var data = await ExtractDataAsync(source);

        // Transform data
        var transformed = await TransformDataAsync(data, target.Format);

        // Load data to target
        var result = await LoadDataAsync(target, transformed);

        return result;
    }
}

ESB Pattern Implementation

Implement ESB pattern:

public class ESBIntegration
{
    public async Task<IntegrationResult> ProcessMessageAsync(IntegrationMessage message)
    {
        // Route message
        var route = await DetermineRouteAsync(message);

        // Transform message
        var transformed = await TransformMessageAsync(message, route);

        // Send to destination
        var result = await SendToDestinationAsync(route.Destination, transformed);

        return result;
    }
}

API Gateway Pattern Implementation

Implement API Gateway pattern:

public class APIGatewayIntegration
{
    public async Task<ApiResponse> ProcessRequestAsync(ApiRequest request)
    {
        // Authenticate request
        var authResult = await AuthenticateRequestAsync(request);
        if (!authResult.Success)
        {
            return new ApiResponse { StatusCode = 401 };
        }

        // Route to backend service
        var backend = await RouteToBackendAsync(request);

        // Forward request
        var response = await ForwardRequestAsync(backend, request);

        // Transform response
        return await TransformResponseAsync(response);
    }
}

Integration Monitoring

Integration Health Monitoring

Monitor integration health:

public class IntegrationHealthMonitor
{
    public async Task<HealthStatus> CheckHealthAsync(string integrationId)
    {
        var recentActivity = await GetRecentActivityAsync(integrationId, TimeSpan.FromMinutes(5));

        return new HealthStatus
        {
            IntegrationId = integrationId,
            IsHealthy = recentActivity.All(a => a.Success),
            ErrorRate = (double)recentActivity.Count(a => !a.Success) / recentActivity.Count,
            LastActivity = recentActivity.LastOrDefault()?.Timestamp,
            Throughput = recentActivity.Count / TimeSpan.FromMinutes(5).TotalSeconds
        };
    }
}

Integration Performance Monitoring

Monitor integration performance:

public class IntegrationPerformanceMonitor
{
    public async Task<PerformanceMetrics> GetMetricsAsync(
        string integrationId, 
        TimeSpan period)
    {
        var activities = await GetActivitiesAsync(integrationId, period);

        return new PerformanceMetrics
        {
            IntegrationId = integrationId,
            TotalActivities = activities.Count,
            AverageLatency = activities.Average(a => a.Latency),
            P95Latency = CalculatePercentile(activities.Select(a => a.Latency), 0.95),
            Throughput = activities.Count / period.TotalSeconds
        };
    }
}

Integration Testing

Integration Test Framework

Test integration scenarios:

public class IntegrationTestFramework
{
    public async Task<TestResults> RunIntegrationTestsAsync()
    {
        var tests = await GetIntegrationTestsAsync();
        var results = new List<TestResult>();

        foreach (var test in tests)
        {
            var result = await RunTestAsync(test);
            results.Add(result);
        }

        return new TestResults
        {
            TotalTests = results.Count,
            PassedTests = results.Count(r => r.Passed),
            FailedTests = results.Count(r => !r.Passed),
            ExecutionTime = results.Sum(r => r.ExecutionTime)
        };
    }
}

Integration Architecture Best Practices Summary

Implementation Checklist

• Analyze integration requirements
• Choose appropriate patterns (EAI/ESB/API Gateway)
• Design integration architecture
• Implement integration layer
• Set up monitoring and logging
• Test integration scenarios
• Document architecture decisions
• Review architecture regularly
• Optimize performance
• Plan for evolution

Production Deployment

Before deploying integration:

1. Test all integration patterns
2. Verify message routing
3. Test transformation logic
4. Validate error handling
5. Set up monitoring
6. Load test the system
7. Document procedures
8. Review security settings

Integration Architecture Troubleshooting

Common Issues

Troubleshoot integration issues:

public class IntegrationTroubleshooter
{
    public async Task<DiagnosticsResult> DiagnoseAsync(string integrationId)
    {
        var diagnostics = new DiagnosticsResult();

        // Check integration status
        diagnostics.IntegrationActive = await CheckIntegrationStatusAsync(integrationId);

        // Check message flow
        diagnostics.MessageFlowWorking = await TestMessageFlowAsync(integrationId);

        // Check transformation
        diagnostics.TransformationWorking = await TestTransformationAsync(integrationId);

        // Check error handling
        diagnostics.ErrorHandlingWorking = await TestErrorHandlingAsync(integrationId);

        return diagnostics;
    }
}

Integration Architecture Evolution

Migration Strategies

Migrate between integration patterns:

public class IntegrationMigration
{
    public async Task MigrateFromEaiToEsbAsync(string integrationId)
    {
        // Phase 1: Set up ESB alongside EAI
        await SetupESBAsync(integrationId);

        // Phase 2: Route new messages to ESB
        await RouteNewMessagesToESBAsync(integrationId);

        // Phase 3: Migrate existing messages
        await MigrateExistingMessagesAsync(integrationId);

        // Phase 4: Decommission EAI
        await DecommissionEAIAsync(integrationId);
    }
}

Integration Architecture Decision Framework

Pattern Selection Guide

Choose the right pattern:

public class IntegrationPatternSelector
{
    public IntegrationPattern SelectPattern(IntegrationRequirements requirements)
    {
        // Simple point-to-point integration
        if (requirements.SystemCount <= 2 && 
            requirements.TransformationComplexity == Complexity.Low)
        {
            return IntegrationPattern.EAI;
        }

        // Complex multi-system orchestration
        if (requirements.SystemCount > 5 || 
            requirements.RequiresOrchestration)
        {
            return IntegrationPattern.ESB;
        }

        // Public API exposure
        if (requirements.RequiresPublicApi || 
            requirements.RequiresApiManagement)
        {
            return IntegrationPattern.APIGateway;
        }

        // Hybrid approach
        return IntegrationPattern.Hybrid;
    }
}

Architecture Comparison

Compare integration architectures:

public class ArchitectureComparator
{
    public ComparisonResult CompareArchitectures(
        IntegrationPattern pattern1, 
        IntegrationPattern pattern2)
    {
        return new ComparisonResult
        {
            Complexity = CompareComplexity(pattern1, pattern2),
            Performance = ComparePerformance(pattern1, pattern2),
            Scalability = CompareScalability(pattern1, pattern2),
            Cost = CompareCost(pattern1, pattern2),
            Maintenance = CompareMaintenance(pattern1, pattern2)
        };
    }
}

Integration Architecture Patterns Deep Dive

EAI Implementation Details

Detailed EAI implementation:

public class EAIImplementation
{
    public async Task<IntegrationResult> IntegrateAsync(
        SourceSystem source, 
        TargetSystem target)
    {
        // Step 1: Extract
        var sourceData = await ExtractFromSourceAsync(source);

        // Step 2: Transform
        var transformedData = await TransformDataAsync(
            sourceData, 
            source.Format, 
            target.Format);

        // Step 3: Validate
        var validationResult = await ValidateDataAsync(transformedData, target);
        if (!validationResult.IsValid)
        {
            return new IntegrationResult
            {
                Success = false,
                Errors = validationResult.Errors
            };
        }

        // Step 4: Load
        var loadResult = await LoadToTargetAsync(target, transformedData);

        return loadResult;
    }
}

ESB Implementation Details

Detailed ESB implementation:

public class ESBImplementation
{
    public async Task<IntegrationResult> ProcessMessageAsync(IntegrationMessage message)
    {
        // Step 1: Receive message
        var received = await ReceiveMessageAsync(message);

        // Step 2: Validate message
        var validation = await ValidateMessageAsync(received);
        if (!validation.IsValid)
        {
            await SendToDeadLetterAsync(received, validation.Errors);
            return new IntegrationResult { Success = false };
        }

        // Step 3: Route message
        var route = await DetermineRouteAsync(received);

        // Step 4: Transform message
        var transformed = await TransformMessageAsync(received, route);

        // Step 5: Send to destination
        var result = await SendToDestinationAsync(route.Destination, transformed);

        return result;
    }
}

API Gateway Implementation Details

Detailed API Gateway implementation:

public class APIGatewayImplementation
{
    public async Task<ApiResponse> ProcessRequestAsync(ApiRequest request)
    {
        // Step 1: Authenticate
        var auth = await AuthenticateAsync(request);
        if (!auth.Success)
        {
            return new ApiResponse { StatusCode = 401 };
        }

        // Step 2: Authorize
        var authz = await AuthorizeAsync(request, auth.User);
        if (!authz.Success)
        {
            return new ApiResponse { StatusCode = 403 };
        }

        // Step 3: Rate limit
        var rateLimit = await CheckRateLimitAsync(request);
        if (!rateLimit.Allowed)
        {
            return new ApiResponse { StatusCode = 429 };
        }

        // Step 4: Route
        var backend = await RouteToBackendAsync(request);

        // Step 5: Forward
        var response = await ForwardRequestAsync(backend, request);

        // Step 6: Transform
        return await TransformResponseAsync(response);
    }
}

Integration Architecture Monitoring

Integration Health Monitoring

Monitor integration health:

public class IntegrationHealthMonitor
{
    public async Task<HealthStatus> GetIntegrationHealthAsync(string integrationId)
    {
        var health = new HealthStatus
        {
            IntegrationId = integrationId,
            Status = HealthStatus.Healthy
        };

        // Check message processing
        var messageHealth = await CheckMessageProcessingAsync(integrationId);
        if (!messageHealth.IsHealthy)
        {
            health.Status = HealthStatus.Unhealthy;
            health.Issues.Add("Message processing issues");
        }

        // Check connectivity
        var connectivityHealth = await CheckConnectivityAsync(integrationId);
        if (!connectivityHealth.IsHealthy)
        {
            health.Status = HealthStatus.Unhealthy;
            health.Issues.Add("Connectivity issues");
        }

        // Check performance
        var performanceHealth = await CheckPerformanceAsync(integrationId);
        if (!performanceHealth.IsHealthy)
        {
            health.Status = HealthStatus.Degraded;
            health.Warnings.Add("Performance degradation");
        }

        return health;
    }
}

Integration Metrics Collection

Collect integration metrics:

public class IntegrationMetricsCollector
{
    public async Task<IntegrationMetrics> CollectMetricsAsync(
        string integrationId, 
        TimeSpan period)
    {
        var metrics = await GetMetricsDataAsync(integrationId, period);

        return new IntegrationMetrics
        {
            IntegrationId = integrationId,
            Period = period,
            TotalMessages = metrics.Sum(m => m.MessageCount),
            SuccessfulMessages = metrics.Count(m => m.Success),
            FailedMessages = metrics.Count(m => !m.Success),
            AverageLatency = metrics.Average(m => m.Latency),
            P95Latency = CalculatePercentile(metrics.Select(m => m.Latency), 0.95),
            Throughput = metrics.Sum(m => m.MessageCount) / period.TotalSeconds
        };
    }
}

Integration Architecture Testing

Integration Test Framework

Test integration architecture:

public class IntegrationTestFramework
{
    public async Task<TestResults> RunIntegrationTestsAsync(string integrationId)
    {
        var tests = new List<IntegrationTest>();

        // Test connectivity
        tests.Add(await TestConnectivityAsync(integrationId));

        // Test message flow
        tests.Add(await TestMessageFlowAsync(integrationId));

        // Test transformation
        tests.Add(await TestTransformationAsync(integrationId));

        // Test error handling
        tests.Add(await TestErrorHandlingAsync(integrationId));

        // Test performance
        tests.Add(await TestPerformanceAsync(integrationId));

        return new TestResults
        {
            IntegrationId = integrationId,
            TotalTests = tests.Count,
            PassedTests = tests.Count(t => t.Passed),
            FailedTests = tests.Count(t => !t.Passed),
            Tests = tests
        };
    }
}

Integration Load Testing

Perform load testing:

public class IntegrationLoadTester
{
    public async Task<LoadTestResults> RunLoadTestAsync(
        string integrationId, 
        int concurrentUsers, 
        TimeSpan duration)
    {
        var results = new List<LoadTestResult>();

        for (int i = 0; i < concurrentUsers; i++)
        {
            var result = await SimulateLoadAsync(integrationId, duration);
            results.Add(result);
        }

        return new LoadTestResults
        {
            IntegrationId = integrationId,
            ConcurrentUsers = concurrentUsers,
            Duration = duration,
            TotalRequests = results.Sum(r => r.RequestCount),
            SuccessfulRequests = results.Count(r => r.Success),
            FailedRequests = results.Count(r => !r.Success),
            AverageResponseTime = results.Average(r => r.ResponseTime),
            P95ResponseTime = CalculatePercentile(
                results.Select(r => r.ResponseTime), 0.95)
        };
    }
}

Integration Architecture Best Practices Summary

Key Takeaways

1. Choose the Right Pattern: EAI for simple integrations, ESB for complex orchestration, API Gateway for public APIs
2. Plan for Scalability: Design integrations to handle growth
3. Implement Monitoring: Track integration health and performance
4. Handle Errors Gracefully: Implement proper error handling and retry logic
5. Test Thoroughly: Test integrations under various conditions

Pattern Selection Guide

• EAI: Simple point-to-point integrations, low transformation complexity
• ESB: Complex multi-system orchestration, high transformation needs
• API Gateway: Public API exposure, API management requirements
• Hybrid: Combine patterns for complex scenarios

Common Pitfalls to Avoid

• Not choosing the right integration pattern
• Failing to plan for scalability
• Not implementing proper monitoring
• Poor error handling and retry logic
• Insufficient testing before deployment

Integration Architecture Implementation Checklist

Pre-Implementation

• Choose integration pattern (EAI, ESB, API Gateway)
• Design integration architecture
• Plan for scalability and performance
• Design error handling and retry logic
• Plan monitoring and observability

Implementation

• Implement integration components
• Configure message routing
• Add transformation logic
• Implement error handling
• Add monitoring and logging

Post-Implementation

• Monitor integration health
• Track performance metrics
• Review and optimize
• Update documentation
• Train team on integration patterns

Integration Architecture Troubleshooting Guide

Common Issues

Issue 1: Integration performance issues

• Symptom: Slow message processing
• Solution: Optimize transformation, add caching, scale horizontally
• Prevention: Design for performance from the start

Issue 2: Message routing failures

• Symptom: Messages not reaching destination
• Solution: Check routing configuration and message format
• Prevention: Test routing thoroughly before production

Issue 3: Transformation errors

• Symptom: Messages failing transformation
• Solution: Validate message format, improve transformation logic
• Prevention: Implement comprehensive message validation

For more integration guidance, explore our Enterprise Service Bus Patterns or API Gateway Comparison.