enterprise architecture for a personal banking use case on Azure Cloud,

✅ 1. Business Overview – Personal Banking Platform

A scalable digital banking platform offering savings/current accounts, fund transfers, personal loans, credit cards, account statements, and personalized financial insights.

⚠️ 2. Risk Categories and Mitigation Plans

Risk Category	Risk Example	Mitigation Strategy
Business	Product-market mismatch, new competitor	Continuous market analysis, customer feedback loop, agile roadmap
Operations	Downtime of transaction systems	Active-active setup with failover, disaster recovery, SLAs, runbooks
Environmental	Azure regional failure	Multi-AZ & Multi-region deployment, Azure Traffic Manager
Technology	Kafka/topic overload, API versioning issues	Rate limiting, topic partitioning, API Gateway with lifecycle mgmt.
Security	Unauthorized access, data breaches	Azure AD, SSO, firewall, NSGs, Istio mTLS, SSL termination, encryption
Compliance	GDPR, RBI regulations non-compliance	Audit trails, data masking, DLP, logging, periodic compliance reviews
People	Key resource attrition, access misuse	RBAC, regular training, cross-functional documentation, principle of least privilege

📘 3. Capabilities and Capability → Application Mapping

Capability	Service/Application
Customer Onboarding	KYC Service, Document Verification, Identity Check
Account Management	Account Service, Ledger Service
Funds Transfer	Payment Service, UPI Service, IMPS/NEFT Integration
Personal Loans	Loan Origination Service, Credit Scoring Engine
Fraud Detection	Risk Analysis Engine, Fraud Monitor Service
Notifications	Email/SMS Notification Service
Account Insights	Analytics Engine, Spending Pattern Service
Audit and Reporting	Audit Trail Service, Reporting Service
Authentication & Access	Auth Service (Azure AD + SSO), RBAC Service

🧱 4. High-Level Technology Stack

Layer	Technology / Service
Frontend	React / Angular
Backend	Spring Boot microservices
Containerization	Docker, stored in Azure Container Registry (ACR)
Orchestration	Azure Kubernetes Service (AKS)
Messaging/Eventing	Kafka (internal), Azure Event Hub (external systems)
API Gateway	Azure API Management (rate limiting, versioning, monitoring)
Data Storage	Azure SQL (relational), Cosmos DB (NoSQL), Azure Blob (file/KYC uploads)
CI/CD	Azure DevOps (code to deployment pipeline)
Monitoring & Logging	Azure Monitor, Application Insights, Log Analytics
Identity & Security	Azure Active Directory, SSO, RBAC, Istio (mTLS, policies), SSL on Load Balancer
Networking & Security	VPC, Subnet (App, DB, Kafka), Firewall, NSG, Load Balancer, DNS, Traffic Manager
Observability	App Insights, Prometheus/Grafana (if custom), Alert Rules, Dashboards

🔗 5. Integration & Connectivity

• VNet: Central virtual network with address space broken into subnets:

  • App Subnet (AKS)

  • Data Subnet (Azure SQL, Cosmos DB)

  • Kafka/Event Hub Subnet

• NSGs: Applied to subnets for traffic filtering

• Firewall: Securing external traffic before hitting Load Balancer

• SSL: Terminated at Load Balancer with TLS 1.2+

• API Gateway: External traffic flows through Azure API Management

• AKS + Istio:

  • Istio for traffic routing, retries, timeouts, mTLS, observability

• DNS Mapping: Domain routes (e.g., api.bank.com) to Load Balancer via Azure DNS

• Traffic Manager: Multi-region AKS clusters managed by Traffic Manager

• Kafka:

  • Internal event bus across services (transaction events, fraud signals)

  • Azure Event Hub for external ingest (e.g., third-party KYC, payment gateway)

• DevOps:

  • Azure DevOps pipeline triggers from code check-in → build → containerization → deploy to AKS

  • Helm charts for AKS deployments

🧩 6. Spring Boot Microservices Components

Service Name	Description
auth-service	AuthN/Z integrated with Azure AD
customer-service	Customer profiles, preferences
account-service	Account operations, balance, transactions
kyc-service	KYC doc collection, OCR, validation
loan-service	Loan applications, eligibility, EMI computation
payment-service	UPI/NEFT/RTGS integration
fraud-service	Detect anomalies using AI/ML models
analytics-service	Spending insights, dashboards
notification-service	Email/SMS alerts
reporting-service	User/downloadable statements, MIS reports

🛡 7. Security and Governance

• Azure AD: Handles user identities + role-based access

• SSO: Integrated for both customer and internal users

• Istio: Enforces zero-trust with mTLS and fine-grained policies

• Key Vault: Secrets, certificates, keys for services

• Audit Logging: Application logs + Azure logs aggregated in Log Analytics

• Encryption: Data at rest (Azure SQL TDE), in transit (TLS), config secrets via Key Vault

  
  

📊 8. High Availability, Scalability, Observability

• Multi-AZ AKS deployments

• Traffic Manager handles global traffic failover

• Kafka with partitions and replication factor for durability

• Azure Monitor: App metrics, logs, custom alerts

• ACR: Used in CI/CD to version containers

• Auto-scaling: HPA in AKS pods, based on CPU/memory thresholds

  
  

Here’s a mock walkthrough of the “Customer Onboarding” user flow in a personal banking platform, covering end-to-end flow from UI to backend services, with components deployed on Azure Cloud using Spring Boot microservices architecture.

✅ Use Case: Customer Onboarding – “Open a New Bank Account”

🧍‍♂️ Actor: End Customer (via Web/Mobile App)

🗺️ 1. Frontend Flow

User Action: Fills onboarding form (name, email, PAN, Aadhaar, address, mobile, etc.) on web/mobile UI.

• Frontend: React app sends form data via HTTPS to api.bank.com/onboarding.

• DNS Routing: api.bank.com resolves via Azure DNS to Azure Load Balancer.

• SSL: TLS terminated at Load Balancer.

• Traffic Flow: Routed to Azure API Management → internal service route.

⚙️ 2. API Gateway Layer (Azure API Management)

• Applies rate limiting (e.g., 100 requests/sec).

• Enforces authentication via Azure AD B2C.

• Routes to backend path: /onboarding-service/onboard-customer.

🛠️ 3. Microservices Orchestration (Spring Boot Services in AKS)

✅ onboarding-service

• Validates payload (format, required fields).

• Calls kyc-service for identity verification.

✅ kyc-service

• Uses Kafka to publish event: kyc.initiated.

• Triggers document collection via external eKYC (NSDL/Aadhaar XML API).

• Fetches PAN status, Aadhaar verification (via external connectors).

• Updates internal status (kyc.verified, kyc.failed).

✅ customer-service

• Creates customer profile: name, DOB, address.

• Stores in Azure SQL.

• Encrypts sensitive fields (Aadhaar/PAN) using Azure Key Vault.

• Emits customer.created event to Kafka.

✅ account-service

• Listens to customer.created event.

• Opens default savings account.

• Initializes ledger balance to ₹0.

• Stores account details in Cosmos DB.

✅ notification-service

• Sends onboarding confirmation email/SMS via Kafka account.created event.

• Uses Azure Logic App or Twilio SendGrid for email.

🔄 4. Event-Driven Interaction (Kafka on Azure)

Event	Consumer Service	Purpose
kyc.initiated	kyc-service	Start verification
customer.created	account-service	Open account
account.created	notification-service	Send welcome notification

Kafka provides asynchronous decoupling, ensuring eventual consistency across services.

🔐 5. Security and Access Control

• All microservices communicate via Istio mTLS.

• Azure AD manages service identities + SSO.

• Access tokens verified at API Gateway and downstream services.

• Secrets (e.g., DB creds, API keys) managed in Azure Key Vault.

🔄 6. Persistence

Data	Service	Store
Customer Profile	customer-service	Azure SQL
Account Info	account-service	Cosmos DB
KYC Status/Docs	kyc-service	Azure Blob + SQL

📈 7. CI/CD and Observability

• Azure DevOps handles deployments of all services to AKS using Helm.

• Logs and metrics collected by Azure Monitor, App Insights.

• Alerts configured on onboarding errors, SLA breaches.

🛡️ 8. Failure Scenarios & Handling

Scenario	Mitigation
eKYC API failure	Retry logic, dead-letter queue, fallback verification
Kafka topic lag	Monitor with Prometheus, alert, increase partitions
DB connectivity loss	Circuit breaker, retries with exponential backoff
KYC takes too long	Timeout + notify user + async recheck

🔚 9. Result

User receives onboarding confirmation and account number via SMS/email. Onboarding status available in UI via polling or event-driven push.

✅ Use Case: UPI Payment Flow – “Send Money to a UPI ID”

🧍‍♂️ Actor: End Customer (via Mobile Banking App)

🗺️ 1. Frontend Interaction

User Action: Opens mobile app → selects “Send Money” → enters recipient UPI ID and amount → authenticates via UPI PIN.

• React Native app triggers API: POST api.bank.com/upi/payment

• Encrypted payload: payer VPA, payee VPA, amount, remarks.

• Token from Azure AD B2C is attached.

🔀 2. API Gateway Layer (Azure API Management)

• Validates token (Azure AD B2C).

• Applies rate-limiting: e.g., 100 req/sec per user/IP.

• Routes request to upi-payment-service inside the AKS cluster via Istio ingress.

⚙️ 3. Microservices (Spring Boot on AKS with Istio)

✅ upi-payment-service

• Performs basic validation (payer balance, UPI ID format).

• Sends event upi.payment.initiated to Kafka.

• Calls upi-auth-service for PIN validation.

✅ upi-auth-service

• Validates encrypted UPI PIN using HSM/Tokenization (Azure Key Vault or Thales HSM).

• Returns success/failure to upi-payment-service.

✅ account-service

• Fetches payer account from Azure SQL or Cosmos DB.

• Ensures sufficient balance.

• Deducts balance (idempotent + ACID).

• Emits upi.debit.success to Kafka.

✅ upi-router-service

• Listens to upi.debit.success.

• Routes payment to NPCI (or PSP gateway like YesBank, PayTM) via HTTPS with signed XML/JSON.

• Handles external payment response.

• Emits final upi.payment.status event (success or failure).

✅ transaction-service

• Logs UPI txn with end-to-end trace ID.

• Sends transaction.recorded event.

✅ notification-service

• Sends SMS/email to payer/payee using Kafka event.

🔄 4. Event Flow on Kafka

Event	Producer	Consumer(s)
upi.payment.initiated	upi-payment-service	auth, account
upi.debit.success	account-service	upi-router-service
upi.payment.status	upi-router-service	notification-service, transaction

🔐 5. Security Layer

• Istio enforces zero-trust (mTLS between services).

• Azure AD token used for frontend/backend auth.

• Token exchange supported for inter-service auth.

• PII data encrypted (Azure Key Vault integration).

• API Gateway applies threat protection rules.

🧮 6. Database & State Handling

Data	Store	Used By
Payer/Payee details	Azure SQL	account-service
UPI Transaction logs	Cosmos DB	transaction-service
Failed Txn retry queue	Kafka DLT	upi-retry-service

🛠️ 7. Reliability Patterns

• Retry: Circuit breakers (Resilience4j) for PSP failure.

• Idempotency key: Ensures duplicate txn requests are not reprocessed.

• DLT (Dead Letter Topic): Captures failed Kafka events.

• Alerting: Azure Monitor + Prometheus + Grafana dashboards.

🧰 8. CI/CD & Infra

• Code in Azure Repos → Build & deploy via Azure DevOps Pipelines.

• Services containerized with Docker → pushed to Azure Container Registry (ACR).

• Deployed via Helm Charts to AKS (Azure Kubernetes Service).

• Istio manages internal traffic, telemetry, retries.

🌐 9. External Integration

• NPCI/UPI API or third-party PSPs.

• Aadhaar/tokenized device fingerprinting.

• Fraud engine (can optionally be triggered here).

📲 10. Final Response to User

• App gets status: Txn Successful or Failed with reason.

• Notification pops: “₹500 sent to abc@upi | Ref: TXN2345 | Time: 11:38 AM”.