Payment platform

A payment system with external providers and cross-service flows.

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System view

Deploy view

Source

payment-platform/system.krs

// Demonstrates: multiple [external] services, complex service topology, deploy diagram
// A payment processing platform integrating with card networks and banks.

@import "theme.krs.style"

system PaymentPlatform {
  label "Payment Platform"

  user Merchant {
    label "Merchant"
    role "Online shops and physical stores using the payment API"
  }

  user PlatformAdmin [human] {
    label "Platform Admin"
    role "Operator handling merchant management and payment monitoring"
  }

  service Gateway {
    label "Payment Gateway"
    description "Accepts payment requests from merchants and controls the processing flow"

    domain Authorization {
      label "Authorization"
      usecase Authorize { label "Authorize a payment" }
      usecase Capture { label "Capture funds" }
      usecase Void { label "Void an authorization" }
    }

    domain Refund {
      label "Refund"
      usecase RequestRefund { label "Request a refund" }
      usecase ProcessRefund { label "Process a refund" }
    }
  }

  service RiskEngine {
    label "Risk Engine"
    description "Fraud detection and transaction scoring"

    domain FraudDetection {
      label "Fraud Detection"
      usecase ScoreTransaction { label "Score a transaction" }
      usecase BlockSuspicious { label "Block suspicious transactions" }
    }
  }

  service Ledger {
    label "Ledger Service"
    description "Records sales, fees, and settlements"

    domain Settlement {
      label "Settlement"
      usecase RecordTransaction { label "Record a transaction" }
      usecase CalculateFee { label "Calculate fees" }
      usecase SettleToMerchant { label "Pay out to the merchant" }
    }
  }

  // External card networks
  service VisaNet [external] {
    label "Visa Net"
    description "Visa card payment network"
  }

  service MasterNet [external] {
    label "Mastercard Network"
    description "Mastercard card payment network"
  }

  // External banking partner
  service BankAPI [external] {
    label "Bank API"
    description "Partner bank handling payouts to merchants"
  }

  // External compliance service
  service ThreeDSecure [external] {
    label "3-D Secure"
    description "3-D Secure authentication service for cardholder verification"
  }

  Merchant       ->  Gateway       "Send a payment request"
  PlatformAdmin  ->  Gateway       "Monitor payment status"
  PlatformAdmin  ->  Ledger        "Review settlement reports"
  Gateway        ->  RiskEngine    "Retrieve a fraud score"
  Gateway        ->  ThreeDSecure  "Verify the cardholder"
  Gateway        ->  VisaNet       "Process Visa payments"
  Gateway        ->  MasterNet     "Process Mastercard payments"
  Gateway       --> Ledger         "Record transactions"
  Ledger        --> BankAPI        "Pay out to merchants"
}

deploy Production {
  label "Production (AWS)"

  // Gateway as an executable JAR (Spring Boot)
  jar "gateway-service" {
    label "Payment Gateway"
    runtime "Java 21 / Spring Boot 3"
    realizes Gateway
  }

  // Risk engine as a container (GPU-enabled scoring)
  oci "risk-engine" {
    label "Risk Engine"
    image "risk-engine:2.0.4"
    runtime "Python 3.12 / FastAPI"
    realizes RiskEngine
  }

  // Lightweight fraud check as a serverless function
  lambda "fraud-check" {
    label "Fraud Check Function"
    runtime "Node.js 22"
    realizes RiskEngine
  }

  // Ledger as a container
  oci "ledger-service" {
    label "Ledger Service"
    image "ledger:1.8.2"
    runtime "Go 1.22"
    realizes Ledger
  }

  // Admin dashboard as a static SPA
  assets "admin-dashboard" {
    label "Admin Dashboard"
    runtime "CloudFront / S3"
  }

  // One-off migration job (no schedule = single run)
  job "ledger-migration" {
    label "Ledger Data Migration"
    runtime "Python 3.12"
  }

  // Daily settlement batch (runs every night at 2am JST)
  job "daily-settlement" {
    label "Daily Settlement Batch"
    schedule "0 17 * * *"
    runtime "Java 21"
    realizes Ledger
  }

  // Monthly fee report
  job "monthly-fee-report" {
    label "Monthly Fee Report"
    schedule "0 2 1 * *"
    runtime "Python 3.12"
    realizes Ledger
  }
}