Orchestrating Financial Transactions with AWS Step Functions

In today's fast-paced financial sector, automation and precise orchestration of transactions can significantly boost efficiency and reliability. AWS Step Functions provides a powerful solution for managing complex workflows by integrating multiple AWS services seamlessly. In this article, we'll explore a real-world financial scenario—loan application processing—and demonstrate how AWS Step Functions can orchestrate these processes efficiently using C#.

Scenario: Loan Application Processing

When a customer applies for a loan, various sequential steps must occur:

• Application submission
• Credit score verification
• Risk assessment
• Decision making
• Notification

AWS Step Functions can orchestrate these steps with clear visualization and robust error handling.

Let's define our workflow:

Start

Verify Credit Score (AWS Lambda)
Perform Risk Assessment (AWS Lambda)
Decision Logic (AWS Lambda)
Notify Customer (AWS Lambda)

End

Implementing the Workflow with AWS Step Functions

Step 1: Define State Machine

{
  "StartAt": "VerifyCreditScore",
  "States": {
    "VerifyCreditScore": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:region:account-id:function:VerifyCreditScore",
      "Next": "RiskAssessment"
    },
    "RiskAssessment": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:region:account-id:function:RiskAssessment",
      "Next": "DecisionMaking"
    },
    "DecisionMaking": {
      "Type": "Choice",
      "Choices": [
        {
          "Variable": "$.riskLevel",
          "StringEquals": "Low",
          "Next": "ApproveLoan"
        },
        {
          "Variable": "$.riskLevel",
          "StringEquals": "High",
          "Next": "DeclineLoan"
        }
      ]
    },
    "ApproveLoan": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:region:account-id:function:NotifyApproval",
      "End": true
    },
    "DeclineLoan": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:region:account-id:function:NotifyDecline",
      "End": true
    }
  }
}

How Transitions Work Between Steps

Transitions between steps in AWS Step Functions occur through clearly defined "Next" parameters. Each state explicitly specifies the next state it should transition to upon completion:

Task States: Perform work using Lambda functions or other AWS services. Upon successful execution, they transition automatically to the next state defined by the "Next" parameter.

Choice States: Evaluate conditions to determine the next state. Choices are evaluated sequentially until a matching condition is found, then the workflow transitions to the corresponding state.

End States: If a state has "End": true, it signifies the termination of the workflow.

AWS Step Functions uses JSON paths to pass output data from one state as input to the next, enabling seamless data flow through the workflow.

C# Implementation (Lambda Functions)

1. Verify Credit Score

public class CreditCheck
{
    public async Task<CreditResponse> Handler(LoanRequest request)
    {
        // Simulate fetching credit score
        int creditScore = await GetCreditScoreAsync(request.CustomerId);
        return new CreditResponse { CreditScore = creditScore };
    }
}

2. Risk Assessment

public class RiskAssessment
{
    public RiskResponse Handler(CreditResponse creditResponse)
    {
        string riskLevel = creditResponse.CreditScore < 700 ? "Low" : "High";
        return new RiskResponse { RiskLevel = riskLevel };
    }
}

3. Notify Customer

Approval Notification

public class NotifyApproval
{
    public async Task Handler(LoanRequest request)
    {
        await EmailService.SendApprovalAsync(request.CustomerEmail);
    }
}

Decline Notification

public class NotifyDecline
{
    public async Task Handler(LoanRequest request)
    {
        await EmailService.SendDeclineAsync(request.CustomerEmail);
    }
}

Benefits

Visibility:
AWS Step Functions provides visual monitoring of each step, simplifying troubleshooting.

Reliability:
Automatic retries and error handling.

Scalability:
Easy integration with various AWS services.