Microservices & Azure Use case

🏦 Use Case: Digital Loan Origination & Management

✳️ Key Capabilities:

• Customer onboarding & KYC

• Loan application and credit scoring

• Risk and fraud detection

• Approval workflow

• Disbursement

• EMI management

• Notifications and customer support

📌 Microservices Breakdown:

Microservice	Responsibility
CustomerService	Customer onboarding, profile, KYC
LoanService	Loan application, product matching
CreditService	Credit scoring, CIBIL check integration
RiskService	Fraud detection, risk profiling
ApprovalService	Loan approval workflow
DisbursementService	Loan disbursement, transaction logging
EMIService	EMI scheduling, repayment, ledger updates
NotificationService	Email/SMS/Push alerts
SupportService	Chatbot and agent escalation
AuthService	Auth via Azure AD (OIDC, OAuth2)

🧱 High-Level Architecture Flow

sql

+--------------------+

| Azure Traffic |

| Manager |

+---------+----------+

|

v

+-----------------------------+

| Azure API Management (APIM) |

+-------------+---------------+

|

v

+----------------------------+

| Azure Kubernetes Service |

| (AKS Cluster) |

+----------------------------+

|

+----------------------------------------------------+

| Istio Service Mesh (Envoy Proxy) |

+----------------------------------------------------+

| | | | |

Customer LoanService CreditService ... Notification

Service ... Service Service etc.

- All services use mTLS, retries, circuit breakers via Istio

- Observability through Istio + Azure Monitor + Prometheus

🔐 Security Architecture

Layer	Control
Auth	Azure Active Directory + OIDC (via Azure AD App Registration)
API Security	Azure APIM validates JWT tokens and scopes
mTLS	Istio enforces encrypted service-to-service communication
RBAC	Kubernetes RBAC for pod-level access
Network	Azure VNET with NSG + private subnets for AKS
Secrets	Azure Key Vault + CSI driver in AKS

🧩 Integration & Messaging

• Azure Event Hub / Kafka on HDInsight – used for event-driven messaging (e.g., loan events, fraud alerts)

• Azure SQL / Cosmos DB – backend per microservice (polyglot persistence)

• Azure Blob Storage – store documents (KYC, loan agreements)

• External Integrations – CIBIL API, GSTN, Aadhaar KYC (via secured APIs)

🔄 DevOps & Observability Stack

Function	Tools Used
CI/CD	Azure DevOps Pipelines + YAML for multi-stage pipelines
Container Registry	Azure Container Registry (ACR)
Monitoring	Azure Monitor + Log Analytics + Prometheus + Grafana
Logging	FluentD + ELK stack + Application Insights
Tracing	OpenTelemetry + Jaeger
Secrets Management	Azure Key Vault
Helm	Helm Charts for AKS deployments
Istio Add-ons	Kiali, Jaeger, Grafana, Prometheus for mesh observability

🧬 Azure Services Mapping

Component	Azure Service Used
Container Orchestration	Azure Kubernetes Service (AKS)
Networking + VPC	Azure VNET, NSG, Subnets
API Gateway	Azure API Management (APIM)
Identity & Auth	Azure Active Directory (Azure AD)
Messaging	Azure Event Hub / Kafka on HDInsight
Database	Azure SQL, Cosmos DB
CI/CD	Azure DevOps
Container Registry	Azure Container Registry (ACR)
Monitoring & Logs	Azure Monitor, Log Analytics, Prometheus
Document Storage	Azure Blob Storage
Secrets	Azure Key Vault

🔁 Workflow Example: Loan Application

1. User logs in via Azure AD B2C, JWT is issued.

2. API call goes through Azure Traffic Manager → APIM → AKS.

3. CustomerService collects profile + KYC.

4. Sends data to CreditService via Kafka.

5. CreditService calls external APIs (e.g., CIBIL).

6. Result sent to RiskService, triggers rules.

7. If eligible, ApprovalService initiates workflow.

8. DisbursementService posts to core banking.

9. EMIService schedules repayments.

10. NotificationService alerts the customer.

Here’s a Hands-On / Whiteboard Exercise for Designing and Deploying a Secure Customer Onboarding Microservice using Spring Boot, Azure Cloud, Kubernetes (AKS), Istio, and full enterprise-grade security practices.

✅ Whiteboard/Interview Prompt:

Design and Deploy a Secure Customer Onboarding Microservice"Design a microservice that handles customer onboarding in a digital banking platform. It should validate customer information, integrate with KYC services, store customer data securely, and support deployment on Azure Cloud with end-to-end security and observability."

✳️ Expected Whiteboard/Hands-On Design Areas

🔹1. Microservice Architecture Breakdown

➤ Customer Onboarding Microservice (Spring Boot)

• Exposes REST APIs (/register, /kyc, /verify)

• JSON validation and schema enforcement

• Integrates with:

  • KYC Service

  • Notification Service (Email/SMS)

  • CRM / Core Banking Service

  • Identity Verification APIs (e.g., Aadhaar, PAN)

➤ Other Supporting Microservices

• KYC Verification Service

• Notification Service

• Audit Logging Service

• Customer Profile Service

🔹2. Security Integration

Area	Implementation
Authentication	Azure AD (OAuth 2.0 + OpenID Connect) via Istio JWT tokens
Authorization	Role-based access control using Spring Security + Azure AD claims
Secrets Management	Azure Key Vault
API Security	Azure API Management with rate limiting, WAF
Network Security	Azure Firewall, Private Subnets
Encryption	TLS in transit (Istio mTLS), AES256 at rest (Azure SQL + Storage)

🔹3. Azure Services Integration

Service	Purpose
AKS (Azure Kubernetes Service)	Container orchestration
Azure SQL	Persistent storage per service
Azure AD	Auth & identity
Azure API Management	API Gateway with security & throttling
Azure Monitor & Log Analytics	Observability
Azure Key Vault	Secrets and keys
Azure DevOps	CI/CD Pipeline
Azure Container Registry	Store built Docker images
Azure Traffic Manager	Global load balancing
Kafka (Azure Event Hubs)	Async events for onboarding, audit logs

🔹4. Networking Flow

1. User Request hits Traffic Manager, routed to Azure Region.

2. Passes through API Gateway (APIM), with WAF rules.

3. Routed to Istio Ingress Gateway in AKS.

4. Traffic is secured with mTLS.

5. Onboarding Service validates token with Azure AD.

6. Inter-service calls (e.g., to KYC, Notification) via Istio sidecars.

7. Events pushed to Kafka (Event Hubs).

8. Data written to Azure SQL securely.

9. Logs and traces collected by Azure Monitor.

🔹5. CI/CD with Azure DevOps

Pipeline Stages:

1. Build Spring Boot App

2. Run Unit/Contract Tests

3. Build Docker Image → Push to ACR

4. Helm Chart Deployment to AKS

5. Istio Gateway + VirtualService update

6. Smoke Tests + Post-deployment hooks

🔹6. Compliance & Observability

• GDPR: Consent tracking, customer data rights

• Audit Logging: Kafka + Azure Blob or Event Grid

• Dashboards: Azure Monitor + Grafana

• Alerts: Azure Alerts → MS Teams / PagerDuty

📌 Architecture Diagram (Summary)

scss

[User]

↓ HTTPS (OAuth2 Token via Azure AD)

[Azure Traffic Manager]

↓

[Azure API Management (APIM)] -- Rate Limit, Auth

↓

[Istio Ingress Gateway in AKS]

↓ (mTLS + JWT validation)

[Customer Onboarding Service] ─────────┐

↓ Kafka (Event Hub) │

[Azure SQL DB] ←─ KYC Service │

└─→ Notification Service

📦 Bonus: Sample API Contracts

yaml

CopyEdit

# OpenAPI 3.0 Spec (onboarding.yaml) paths: /register: post: summary: Register a new customer requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/NewCustomer' responses: 200: description: Success

🔍 Hands-On Deployment Tasks (Interview or Lab)

• Implement CustomerOnboardingController in Spring Boot.

• Use Spring Security to validate Azure AD token.

• Configure Helm chart with Istio VirtualService & DestinationRule.

• Integrate with Azure SQL using JPA.

• Push container to ACR via Azure DevOps pipeline.

• Deploy to AKS with Helm.