Microservices # Banking Application

 Here is a clear, professional, real-world Banking Microservices Architecture—the same style used in interviews for Java, Spring Boot, and cloud roles.

---

⭐ Banking Microservices Architecture (Text Diagram + Explanation)

Banks usually follow a domain-driven, event-driven, highly secure microservices design.

Below is a full architecture diagram in text (ASCII) followed by component explanations.

---

🏦 Banking Microservices Architecture – Text Diagram

                                ┌─────────────────────────┐
                                │      CLIENT APPS        │
                                │  Mobile / Web / ATM /   │
                                │     Internet Banking     │
                                └───────────▲─────────────┘
                                            │
                                            │ HTTPS / OAuth2
                                            ▼
                            ┌──────────────────────────────────┐
                            │           API GATEWAY            │
                            │  Auth, Routing, Throttling       │
                            │  Logging, Security Policies      │
                            └───────────▲──────────────────────┘
                                        │
    ┌────────────────────────────────────┼────────────────────────────────┐
    │                                    │                                │
    ▼                                    ▼                                ▼
┌────────────────────┐         ┌────────────────────┐          ┌─────────────────────┐
│  CUSTOMER SERVICE   │         │  ACCOUNT SERVICE    │          │ TRANSACTION SERVICE │
│ Profile, KYC, AML   │         │ Savings, Current    │          │ Money Transfer,     │
│ Verification        │         │ Account Lifecycle   │          │ Debit/Credit, Limit │
└──────┬──────────────┘         └──────────┬──────────┘          │ Management          │
       │                                     │                    └─────────┬──────────┘
       ▼                                     ▼                              │
┌──────────────┐                     ┌──────────────┐                       ▼
│ Customer DB  │                     │ Accounts DB  │              ┌───────────────────┐
└──────────────┘                     └──────────────┘              │ Transactions DB   │
                                                                   └───────────────────┘

                    ┌───────────────────────────────┐
                    │        PAYMENT SERVICE        │
                    │  UPI, IMPS, NEFT, RTGS APIs   │
                    └──────────┬────────────────────┘
                               │
                               ▼
                   ┌────────────────────────┐
                   │ External Payment Switch│
                   │ NPCI / Visa / Master   │
                   └────────────────────────┘

          ┌─────────────────────────┐
          │  CARD MANAGEMENT SRV   │
          │  Credit/Debit Card Ops │
          └───────┬────────────────┘
                  │
                  ▼
        ┌────────────────────────────┐
        │ Card Processing Network    │
        │ (Mastercard/Visa)          │
        └────────────────────────────┘


          ┌─────────────────────────┐
          │   LOAN SERVICE          │
          │  EMI, Home Loan, Credit │
          └────────┬────────────────┘
                   │
                   ▼
          ┌──────────────────────────┐
          │      Loan DB             │
          └──────────────────────────┘


          ┌─────────────────────────┐
          │ NOTIFICATION SERVICE    │
          │ SMS, Email, WhatsApp    │
          └────────┬────────────────┘
                   │
                   ▼
        ┌──────────────────────────┐
        │ SMTP / SMS Gateways      │
        └──────────────────────────┘


─────────────────────────────────────────────────────────────────────────────
                             EVENT-DRIVEN LAYER
─────────────────────────────────────────────────────────────────────────────

                         ┌─────────────────────────┐
                         │         KAFKA           │
                         │ Topics:                 │
                         │  - ACCOUNT_CREATED      │
                         │  - MONEY_TRANSFERRED    │
                         │  - CARD_BLOCKED         │
                         │  - PAYMENT_SETTLED      │
                         └─────────────────────────┘

   CUSTOMER SVC  → Publishes KYC events  
   ACCOUNT SVC   → Listens to events → Create/update accounts  
   TRANSACTION   → Publishes money-transfer events  
   PAYMENT SVC   → Publishes settlement events  
   NOTIFICATION  → Sends messages based on events  


─────────────────────────────────────────────────────────────────────────────
                         SECURITY & COMPLIANCE LAYER
─────────────────────────────────────────────────────────────────────────────

  ┌──────────────────────┐    ┌──────────────────────┐    ┌───────────────────┐
  │ IAM / OAuth2 / JWT   │    │  Audit Logging        │    │ Compliance (AML)  │
  └──────────────────────┘    └──────────────────────┘    └───────────────────┘

  - MFA (OTP / Biometrics)  
  - Role-based access (RBAC)  
  - Encryption (TLS/SSL, AES-256)  
  - Anti-money laundering checks  
  - Fraud detection engines  


─────────────────────────────────────────────────────────────────────────────
                          OBSERVABILITY & PLATFORM
─────────────────────────────────────────────────────────────────────────────

  ┌─────────────┐   ┌─────────────┐   ┌──────────────┐
  │ Logstash    │ → │ Elasticsearch│ → │ Kibana        │
  └─────────────┘   └─────────────┘   └──────────────┘

  ┌─────────────┐   ┌─────────────┐
  │   Redis      │   │ Prometheus │→Grafana
  └─────────────┘   └─────────────┘

─────────────────────────────────────────────────────────────────────────────
                          DEPLOYMENT LAYER
─────────────────────────────────────────────────────────────────────────────

Docker Containers → Kubernetes (EKS/GKE/AKS/On-Prem)  
CI/CD: Jenkins / GitHub Actions  
Secrets: Vault / KMS  

---

⭐ Short Interview-Ready Explanation (2 minutes)

“In banking, microservices are split by business domains like Customer, Accounts, Transactions, Payments, Loans, Cards, and Notifications.

A request from a mobile or web app goes through an API Gateway that handles routing, authentication (OAuth2), and rate-limiting.

Each service has its own database to ensure loose coupling.
Sensitive operations like Payments or Money Transfers integrate with external systems such as NPCI, Visa, or Mastercard.

Kafka is used for event-driven flows—for example, when an account is created, a KYC event is published; when money is transferred, a transaction event triggers notifications and fraud checks.

The system is monitored with ELK and Prometheus/Grafana, and deployed on Kubernetes with strict security compliance like AML, audit logging, encryption, and MFA.”

---

⭐ Want more?

I can also give you:

✅ High-Level Architecture Diagram
✅ Detailed Low-Level Design (LLD)
✅ Bank Transaction Flow (step-by-step)
✅ Fraud detection microservice design
✅ Interview Q&A for Banking Microservices

Just tell me!