10
Day Delivery
Technical Proposal · Version 1.0
LoanFlow Microservices
Platform
A cloud-native, event-driven microservices architecture for end-to-end loan origination, risk management, approval, and repayment lifecycle management — delivered by a single senior full-stack developer across 10 focused days.
01 — Executive Summary
A Unified, Decoupled Loan Platform
We propose an event-driven microservices platform that decomposes the full loan lifecycle — from customer onboarding to final repayment — into 11 independently deployable, independently scalable backend services communicating over an async message bus, built and delivered by a single senior full-stack developer.
11
Microservices
10
Days to MVP
2
Sprint Cycles
99.9%
Target Uptime SLA
📌 Problem Statement
Traditional monolithic loan platforms suffer from deployment bottlenecks, team coupling, and inability to scale individual stages independently. As loan volume grows, the KYC review, risk management, and repayment services often experience uneven load — demanding isolated scalability that monoliths cannot provide.
✅ Proposed Solution
A fully decomposed microservices architecture aligned 1:1 with each stage of the loan flowchart — each service owning its database, its domain logic, and its REST API surface. Services communicate asynchronously via Kafka events, with a central API Gateway handling routing, auth, and rate limiting. No frontend is in scope — all services expose clean REST APIs consumable by any client.
02 — System Architecture
Event-Driven Service Mesh
All services are independently deployed as Docker containers orchestrated via Kubernetes. Communication uses REST for synchronous queries and Apache Kafka for all state-transition events.
API Consumers (Client-side — out of scope, APIs provided for integration)
Partner API
Postman / API Tests
HTTPS / TLS 1.3
Gateway & Cross-Cutting
API Gateway
Auth · Rate Limit · Routing
Auth · Rate Limit · Routing
Auth Service
JWT · OAuth2 · RBAC
JWT · OAuth2 · RBAC
Observability
Prometheus · Grafana · Jaeger
Prometheus · Grafana · Jaeger
Config Service
Consul · Vault Secrets
Consul · Vault Secrets
REST + Kafka Events
Core Domain Microservices
Customer
Application
Document
KYC Review
Risk Mgmt
Discussion
Approval
Agreement
Activation
Repayment
Notification
Apache Kafka — Message Bus
Data Layer — Each Service Owns Its Database (Database-per-Service Pattern)
PostgreSQL
Transactional Data
Transactional Data
MongoDB
Documents · KYC Data
Documents · KYC Data
Redis
Sessions · Cache
Sessions · Cache
S3 / MinIO
File Storage
File Storage
Elasticsearch
Search · Audit Logs
Search · Audit Logs
Figure 1 — High-level system architecture. Each domain microservice has its own isolated data store (Database-per-Service pattern) and communicates state changes via Kafka topics.
03 — Microservices Breakdown
11 Domain Services
Each service maps directly to a stage in the loan lifecycle flowchart. Click any service card to expand its full specification.
Customer Service
Port 8001 · Stage: Input
Manages customer registration, login, profile management, and KYC data collection. Entry point for all new borrowers.
POST /register
POST /login
GET /profile
PUT /kyc
Loan Application Service
Port 8002 · Stage: Input
Handles loan application creation, linking customers to projects, entering facility details, and tracking application lifecycle status.
POST /applications
GET /applications/:id
PUT /applications/:id
GET /applications/status
Document Service
Port 8003 · Stage: Input
Handles secure document upload, storage, versioning, retrieval, and validation for all KYC and project documents.
POST /documents/upload
GET /documents/:id
DELETE /documents/:id
GET /documents/list
KYC Review Service
Port 8004 · Stage: Review
Orchestrates the KYC team review workflow — customer identity verification, compliance checks, project feasibility, and document validation.
POST /kyc/assign
PUT /kyc/verify
POST /kyc/decision
GET /kyc/queue
Risk Management Service
Port 8005 · Stage: Risk
Performs financial analysis, risk scoring, repayment capacity assessment and generates a risk-rated recommendation for loan discussion.
POST /risk/assess
GET /risk/score/:id
POST /risk/decision
GET /risk/report/:id
Loan Discussion Service
Port 8006 · Stage: Discussion
Manages the negotiation stage — recording interest rate discussions, loan amount & tenure, repayment terms, and capturing customer offer acceptance/rejection.
POST /discussion/start
PUT /discussion/offer
POST /discussion/accept
POST /discussion/decline
Final Approval Service
Port 8007 · Stage: Approval
Manages the multi-level approval workflow — internal approval, management approval, final assessment, and ultimate go/no-go decision.
POST /approval/submit
PUT /approval/internal
PUT /approval/management
POST /approval/final
Agreement Service
Port 8008 · Stage: Doc & Activation
Generates the loan agreement document, facilitates e-signing, and stores the signed copy securely for legal and compliance records.
POST /agreement/generate
POST /agreement/esign
POST /agreement/upload
GET /agreement/:id
Loan Activation Service
Port 8009 · Stage: Doc & Activation
Activates the loan account upon agreement signing, creates the repayment schedule, and initiates disbursement workflows.
POST /activation/trigger
GET /activation/schedule/:id
GET /activation/account/:id
POST /activation/disburse
Repayment Service
Port 8010 · Stage: Repayment
Processes customer payments, verifies payment proof, tracks outstanding balance, detects overdue instalments, and manages loan closure upon full repayment.
POST /payments
POST /payments/proof
GET /payments/history
GET /payments/outstanding
Notification Service
Port 8011 · Cross-Cutting
Consumes events from all services and delivers multi-channel notifications — email, SMS, push, and in-app — for every status change in the loan lifecycle.
GET /notifications/inbox
PUT /notifications/read
POST /notifications/preferences
GET /notifications/history
04 — Delivery Plan
2-Sprint Agile Execution (10 Days)
Deliverables are organized into two 5-day sprints, all owned by a single senior full-stack developer. Each sprint ends with a working API demo, Postman collection handover, and acceptance criteria sign-off.
SPRINT 1
Days 1–5
Foundation + Input + Review + Risk
SPRINT 2
Days 6–10
Discussion + Approval + Activation + Repayment
SPRINT 1
Foundation, Infrastructure & Input Services
Days 1–5
▼
✓Set up Kubernetes cluster & namespaces
✓Configure API Gateway (Kong / Traefik)
✓Deploy Kafka & create all topics
✓Auth Service (JWT, RBAC, OAuth2)
✓Customer Service — full CRUD + KYC fields
✓Loan Application Service — state machine
✓Document Service — upload + S3 integration
✓CI/CD pipeline (GitHub Actions / ArgoCD)
✓Postgres & MongoDB schemas & migrations
✓Unit tests ≥ 80% coverage for Sprint 1 services
Sprint Deliverables:
Working registration + login
Loan application creation
Document upload to S3
Kafka event bus live
All services dockerized
SPRINT 2
KYC, Risk, Approval, Agreement, Activation, Repayment & Hardening
Days 6–10
▼
✓KYC Review Service — assignment & decision gates
✓Risk Management Service — scoring engine
✓Loan Discussion Service — offer engine + versioning
✓Final Approval Service — 3-level workflow
✓Agreement Service — PDF generation + e-sign
✓Loan Activation Service — schedule calculation
✓Repayment Service — payment capture + verification
✓Notification Service — Kafka consumer + email/SMS
✓Rejection path — all 3 rejection scenarios
✓Overdue detection & reminder automation
✓Full E2E regression suite (all 11 services)
✓Security audit (OWASP Top 10 checklist)
✓API documentation (Swagger / OpenAPI 3.0)
✓Observability: Prometheus + Grafana dashboards live
✓UAT deployment + client demo & sign-off
Sprint Deliverables:
KYC workflow end-to-end
Risk score computation
Offer accept/reject flow
3-tier approval chain
Signed agreement PDF
Live repayment schedule
Full payment loop
Email + SMS notifications
Swagger docs live
UAT sign-off ready
05 — API Design
RESTful API Contracts
All APIs conform to REST conventions, use JSON payloads, are versioned under /api/v1/, and are secured with Bearer JWT tokens via the API Gateway.
| Method | Endpoint | Service | Description | Auth |
|---|---|---|---|---|
| POST | /api/v1/customers/register | Customer | Register new customer account | Public |
| POST | /api/v1/auth/login | Auth | Authenticate, returns JWT + refresh token | Public |
| GET | /api/v1/customers/{id}/profile | Customer | Fetch customer profile & KYC status | Bearer |
| PUT | /api/v1/customers/{id}/kyc | Customer | Submit / update KYC details | Bearer |
| POST | /api/v1/applications | Application | Create new loan application | Bearer |
| GET | /api/v1/applications/{id} | Application | Get application + current stage | Bearer |
| GET | /api/v1/applications/{id}/timeline | Application | Full audit trail / stage history | Bearer |
| POST | /api/v1/documents/upload | Document | Multipart upload of required docs | Bearer |
| GET | /api/v1/documents/{appId}/list | Document | List all documents for application | Bearer |
| DELETE | /api/v1/documents/{docId} | Document | Remove uploaded document | Bearer |
| Method | Endpoint | Service | Description | Auth |
|---|---|---|---|---|
| GET | /api/v1/kyc/queue | KYC Review | Get pending KYC review queue (officer view) | OFFICER |
| POST | /api/v1/kyc/{appId}/assign | KYC Review | Assign application to KYC officer | MANAGER |
| PUT | /api/v1/kyc/{appId}/verify | KYC Review | Submit verification checklist results | OFFICER |
| POST | /api/v1/kyc/{appId}/decision | KYC Review | Approve or reject (with reason) | MANAGER |
| POST | /api/v1/risk/{appId}/assess | Risk Mgmt | Trigger risk assessment computation | SYSTEM |
| GET | /api/v1/risk/{appId}/report | Risk Mgmt | Retrieve full risk assessment report | OFFICER |
| POST | /api/v1/risk/{appId}/decision | Risk Mgmt | Risk team approve/reject for discussion | RISK_MGR |
| POST | /api/v1/discussion/{appId}/offer | Discussion | Send loan offer to customer | OFFICER |
| POST | /api/v1/discussion/{appId}/accept | Discussion | Customer accepts the offer | Bearer |
| POST | /api/v1/discussion/{appId}/decline | Discussion | Customer declines — triggers CLOSE | Bearer |
| POST | /api/v1/approval/{appId}/internal | Approval | Internal level approval action | INTERNAL |
| POST | /api/v1/approval/{appId}/management | Approval | Management level approval action | MANAGER |
| POST | /api/v1/approval/{appId}/final | Approval | Credit committee final decision | CREDIT_HEAD |
| Method | Endpoint | Service | Description | Auth |
|---|---|---|---|---|
| POST | /api/v1/agreement/{appId}/generate | Agreement | Auto-generate loan agreement PDF | SYSTEM |
| POST | /api/v1/agreement/{appId}/esign | Agreement | Initiate e-sign workflow | Bearer |
| POST | /api/v1/agreement/{appId}/upload | Agreement | Upload manually signed copy | Bearer |
| POST | /api/v1/activation/{appId}/trigger | Activation | Activate loan account post-signing | SYSTEM |
| GET | /api/v1/activation/{loanId}/schedule | Activation | Get full EMI repayment schedule | Bearer |
| GET | /api/v1/activation/{loanId}/account | Activation | Get loan account details & balance | Bearer |
| POST | /api/v1/payments | Repayment | Record a payment transaction | Bearer |
| POST | /api/v1/payments/{payId}/proof | Repayment | Upload payment proof (receipt) | Bearer |
| GET | /api/v1/payments/{loanId}/history | Repayment | Full payment history for loan | Bearer |
| GET | /api/v1/payments/{loanId}/outstanding | Repayment | Remaining balance + next EMI due | Bearer |
| POST | /api/v1/loans/{loanId}/close | Repayment | Close loan account on full repayment | SYSTEM |
| Method | Endpoint | Service | Description | Auth |
|---|---|---|---|---|
| GET | /api/v1/notifications/inbox | Notification | Get user notification inbox | Bearer |
| PATCH | /api/v1/notifications/{id}/read | Notification | Mark notification as read | Bearer |
| PUT | /api/v1/notifications/preferences | Notification | Update channel preferences | Bearer |
| POST | /api/v1/auth/refresh | Auth | Refresh JWT access token | Refresh Token |
| POST | /api/v1/auth/logout | Auth | Invalidate session tokens | Bearer |
| GET | /health/{service} | All | Health check endpoint (Kubernetes liveness) | Internal |
| GET | /metrics | All | Prometheus metrics scrape endpoint | Internal |
| GET | /api/v1/admin/loans | Application | Admin: list all loans with filters | ADMIN |
| GET | /api/v1/admin/reports/dashboard | Application | Admin: aggregate pipeline metrics (API response) | ADMIN |
06 — Technology Stack
Modern, Battle-Tested Technologies
Backend Services
Java 21 + Spring Boot 3
Node.js 20 + Express
Python 3.12 + FastAPI
REST + OpenAPI 3.0
gRPC (internal calls)
Data Stores
PostgreSQL 16
MongoDB 7.0
Redis 7.2
Elasticsearch 8
MinIO (S3-compatible)
Messaging & Comms
Apache Kafka 3.7
SendGrid (Email)
Twilio (SMS)
Firebase FCM (Push)
WebSocket (Real-time)
Infrastructure
Docker + Kubernetes
Helm Charts
ArgoCD (GitOps)
GitHub Actions (CI)
Terraform (IaC)
Security
JWT + OAuth2 / OIDC
HashiCorp Vault
mTLS (service mesh)
Istio Service Mesh
OWASP ZAP (scanning)
Observability
Prometheus + Grafana
Jaeger (Tracing)
ELK Stack (Logging)
PagerDuty (Alerting)
k6 (Load Testing)
API Gateway
Kong Gateway
Rate Limiting
Circuit Breaker
SSL Termination
Request Logging
Docs & Testing
Swagger / OpenAPI 3.0
Postman Collections
Jest / JUnit
Testcontainers
k6 (Load Testing)
07 — Non-Functional Requirements
SLA, Performance & Quality Targets
⚡ Performance
API response times and system throughput targets under normal operating conditions.
P95 API Latency< 300ms
P99 API Latency< 800ms
Kafka Event Latency< 50ms
Concurrent Users1,000+
Applications/day10,000+
🛡️ Availability
Uptime SLA targets and disaster recovery objectives per service tier.
Platform Uptime99.9%
Critical Services99.95%
RTO (Recovery)< 30 min
RPO (Data Loss)< 5 min
Kafka ReplicationFactor 3
📈 Scalability
Horizontal scaling capabilities and auto-scaling thresholds per service.
Min Replicas2 per svc
Max Replicas10 per svc
HPA Trigger (CPU)70%
DB Connection Pool50 per pod
Kafka Partitions12 per topic
🔐 Security
Authentication, authorisation, and data protection compliance standards.
Auth ProtocolOAuth2 + JWT
Transport EncryptionTLS 1.3
At-rest EncryptionAES-256
Secrets ManagementVault
OWASP ComplianceTop 10
🧪 Quality
Code quality gates, testing coverage, and deployment pipeline standards.
Unit Test Coverage≥ 80%
Integration TestsFull E2E
Code ReviewMandatory PR
Static AnalysisSonarQube
Zero-downtime DeployBlue/Green
📋 Compliance
Regulatory and data governance requirements for a financial services platform.
Data ResidencyConfigurable
Audit LoggingAll mutations
PII MaskingIn all logs
GDPR ReadyRight to erase
Log Retention7 years
08 — Risk Register
Identified Risks & Mitigations
| # | Risk | Category | Likelihood | Impact | Mitigation |
|---|---|---|---|---|---|
| R1 | Kafka service mesh latency under peak load degrades real-time UX | Technical | Medium | High | Partition tuning, consumer group scaling, dead-letter queues, circuit breakers |
| R2 | Scope creep from undefined KYC compliance rules mid-sprint | Scope | High | Medium | Freeze compliance rules before Sprint 1; formal change request process; buffer in Sprint 2 |
| R3 | Third-party e-sign API integration delays Agreement Service | Integration | Medium | Medium | Mock e-sign service in Sprint 1; real integration in Sprint 2; manual upload fallback built-in |
| R4 | Database-per-service data consistency challenges (saga pattern) | Technical | Medium | High | Choreography-based sagas with compensating transactions; idempotent event consumers |
| R5 | Developer unavailability or illness during 10-day engagement | Resource | Low | High | Documented service contracts and progress commits from Day 1; daily async updates to client; timeline buffer built into Sprint 2 |
| R6 | Kubernetes cluster misconfiguration causing service instability | Infrastructure | Low | Medium | IaC with Terraform + Helm; staging environment mirrors prod; automated health checks |
| R7 | Security vulnerabilities in JWT implementation (token leakage) | Security | Low | High | Short-lived access tokens (15 min), refresh rotation, OWASP scan in CI, Vault for secrets |
09 — Delivery Team
Solo Expert Delivery
This engagement is delivered by a single senior full-stack developer — owning all 11 backend services end-to-end, from architecture and implementation to testing and deployment.
🧑💻
Solo Delivery
Senior Full-Stack Developer
Node.js
Java / Spring Boot
PostgreSQL
MongoDB
Kafka
Redis
Docker
Kubernetes
CI/CD
REST APIs
Microservices