Bounded Context & Microservices

Use Case: Loan Application Processing

A legacy system has PL/SQL packages and Oracle Forms handling:

• Customer KYC

• Credit Score Evaluation

• Loan Eligibility Calculation

• Loan Disbursement

After running VFunction, it suggests candidate service boundaries. SMEs validate these against real business rules.

1️⃣ Define Aggregates (root entities)

Aggregates are clusters of entities that must be treated as a single unit for consistency.

Example:

Aggregate	Description	Root Entity
LoanApplication	Tracks the full loan request	LoanApplication
Customer	KYC, contact info, documents	Customer
CreditEvaluation	Credit checks & score	CreditScoreReport

2️⃣ Define Entities & Value Objects

Entities have identity, Value Objects are immutable and describe attributes.

Example:

Customer Aggregate

• Entity: Customer (has customerId)

• Value Objects:

  • Address (street, city, state, zip)

  • Document (type, number, expiration)

LoanApplication Aggregate

• Entity: LoanApplication (loanId)

• Value Objects:

  • LoanAmount

  • InterestRate

  • Tenure

CreditEvaluation Aggregate

• Entity: CreditScoreReport (reportId)

• Value Objects:

  • Score

  • Rating

3️⃣ Define Bounded Contexts

Bounded Context = a self-contained domain area where entities and rules apply consistently.

Example Bounded Contexts:

Bounded Context	Aggregates	Responsibilities
KYC Context	Customer	Collect & validate customer documents
Credit Context	CreditScoreReport	Call credit bureau, evaluate score
Loan Processing Context	LoanApplication	Calculate eligibility, track loan lifecycle
Disbursement Context	LoanApplication	Approve and disburse loan, generate agreement

4️⃣ Map Bounded Context → Microservice

After defining bounded contexts, each can become a microservice:

Microservice	Bounded Context	Technology / DB
CustomerService	KYC Context	Spring Boot + PostgreSQL / Cosmos DB
CreditService	Credit Context	Spring Boot + Kafka for events
LoanService	Loan Processing Context	Spring Boot + PostgreSQL
DisbursementService	Disbursement Context	Spring Boot + Batch Jobs (EOD), Kafka for events

Event Flow Example:

1. Customer submits KYC → CustomerService validates → publishes KYCCompletedEvent.

2. CreditService consumes event → checks credit score → publishes CreditScoreReadyEvent.

3. LoanService consumes both KYC & CreditScore → calculates eligibility → triggers LoanApprovedEvent.

4. DisbursementService listens → disburses loan → triggers LoanDisbursedEvent.

✅ Key Points

• VFunction gives initial technical boundaries, SMEs validate for business logic.

• DDD ensures aggregates, entities, bounded contexts map to meaningful microservices.

• This approach reduces coupling, improves maintainability, and aligns microservices with real business capabilities.