Student Module Registration Flow in Microservices & Event-Driven Architecture
A Scalable, Resilient Workflow for Academic System
Abstract
This presentation showcases the design and operational flow of a modern Student Module Registration System built on microservices and event-driven architecture. It highlights how services like Student and Registration interact across layers — from validation and transactional persistence to event emission and consumption. Using patterns like CQRS, Saga, and the Outbox, the system ensures atomicity, scalability, and resilience. Real-world scenarios such as student profile creation and module registration illustrate how asynchronous workflows and service orchestration maintain consistency and enable seamless integration with external systems.
📘 Introduction
Academic institutions face intense demand during student registration periods. Students must select subjects, verify availability of teachers and classrooms, complete payments, and receive confirmation — all in real time. This system is designed to handle that complexity through a distributed, event-driven architecture that ensures scalability, reliability, and transactional integrity.
Built using microservices, CQRS, and asynchronous communication, the system supports modular development, fault tolerance, and seamless integration with external services such as payment gateways, email providers, and legacy infrastructure.
🎯 Design Objectives
Scalability: Support thousands of concurrent users during peak registration periods
Modularity: Isolate business domains for independent development and deployment
Resilience: Recover gracefully from partial failures using compensation logic
Observability: Enable full tracing, logging, and metrics across services
Security: Protect sensitive data with secure protocols and access control
Extensibility: Integrate easily with external systems and legacy infrastructure
📄 Case Summary
Students interact with the system through a web or mobile interface. They log in, select subjects based on their academic program, verify availability (teacher/classroom), initiate payment, and receive confirmation via email along with an admission form.
The system must:
Prevent overbooking
Handle payment failures gracefully
Notify students in real time
Integrate with external services
Maintain audit logs for compliance
🧭 Architecture Overview
The system is structured into five distinct layers
Each layer is independently scalable and loosely coupled to promote agility and resilience.
🧱 Layered Architecture
The system is structured into five layers:
1. Presentation Layer Interfaces: Web (React), Mobile (Flutter) Auth: JWT-based authentication Gateway: API Gateway routes requests securely
2. Microservices Layer Services: Student, Subject, Schedule, Registration, Payment, Notification, Admission, Analytics Communication: REST/gRPC (synchronous), Kafka/RabbitMQ (asynchronous) Security: OWASP-aligned practices, RBAC, input sanitization Deployment: Docker containers on Kubernetes with autoscaling
3. Business Logic Layer Orchestration: Saga pattern for distributed transactions Event Handling: Domain events (e.g., StudentCreated, ModuleRegistered) Reliability: Transactional Outbox + CDC for event consistency
4. Integration Layer External Systems: Stripe, SendGrid, S3, Legacy ERP Patterns: Adapter for legacy systems, OAuth for secure APIs
5. Database Layer CQRS: Separate command and query models Polyglot Persistence: PostgreSQL, Redis, Elasticsearch, MongoDB, Couchbase Read Models: Updated via event handlers or CDC streams
🧱 Layer-by-Layer Breakdown
1️⃣ Presentation Layer
What it is: The front-facing interface where students interact with the system via web or mobile apps.
Why it matters: It provides a seamless user experience and acts as the entry point for all operations, ensuring secure and efficient communication with backend services.
How it works:
Built using React (web) and React Native (mobile)
Communicates with backend via API Gateway
Uses JWT tokens for authentication
Handles form submissions, error feedback, and real-time updates
Example: A student logs in, views available subjects, selects one, and initiates registration — all through the UI, which routes requests via the API Gateway.
2️⃣ Microservices Layer
What it is: A collection of independently deployable services, each responsible for a specific business domain.
Why it matters: Enables modular development, fault isolation, and horizontal scalability. Each service is designed around a single responsibility and enforces its own data ownership, security, and operational logic.
How it works:
Services communicate via REST or gRPC
Each service owns its own database
Stateless design with retry, timeout, and circuit breaker logic
Exposes APIs for internal and external consumers
Implements service-level security controls aligned with OWASP Top 10
Service Table:
Student Service
Manages student profiles, academic history, and identity verification
GET /students/{id}
Validates access control using JWT claims; encrypts personal data at rest; sanitizes input fields to prevent injection
Subject Service
Provides subject catalog, prerequisites, and program mappings
GET /subjects?program=BSc-CS
Uses parameterized queries; enforces role-based access; disables debug endpoints in production
Schedule Service
Tracks availability of teachers and classrooms
GET /availability?subjectId=123
Validates query parameters; restricts access to internal metadata; applies rate limiting to prevent abuse
Registration Service
Orchestrates registration workflow and initiates saga coordination
POST /register
Verifies student ownership to prevent IDOR; logs registration attempts; validates payload structure and schema
Payment Service
Integrates with external gateways to process payments
POST /pay
Secures API keys and tokens; validates external URLs; monitors for transaction anomalies and replay attacks
Notification Service
Sends email/SMS confirmations for registration and payment
POST /notify/email
Rate limits outbound messages; validates message templates; logs delivery status for audit and compliance
Admission Service
Generates admission documents post-registration
GET /admission/{studentId}
Enforces access control; protects file storage endpoints; validates document generation requests
Analytics Service
Collects and aggregates system events for reporting and dashboards
POST /events
Ensures integrity of event logs; monitors for injection attempts; secures ingestion endpoints with authentication
Communication Patterns:
Synchronous: REST/gRPC for direct service calls
Asynchronous: Kafka or RabbitMQ for event propagation
Service Mesh (optional): For observability, traffic shaping, and mTLS between services
Resilience Features:
Retry logic with exponential backoff
Timeout and circuit breaker mechanisms
Idempotent endpoints to prevent duplicate processing
3️⃣ Business Logic Layer
What it is: The orchestration layer coordinates workflows and ensures consistency across distributed services.
Why it matters: In a distributed system, operations span multiple services. This layer ensures that multi-step processes (like registration + module enrollment + payment) complete reliably or roll back safely.
How it works:
🔄 Event-Driven Architecture
Services publish and subscribe to domain events via Kafka or RabbitMQ
Events include: SubjectSelected, AvailabilityConfirmed, PaymentConfirmed, RegistrationCompleted
Transactional Outbox ensures events are published only after DB commits
CDC (Change Data Capture) streams DB changes to update read models
🔁 Saga Pattern
Saga Coordinator (in Registration Service) manages distributed transactions
Defines compensation actions for rollback (e.g., cancel seat if payment fails)
Example Flow:
Registration Service emits SubjectSelected
Schedule Service emits AvailabilityConfirmed
Payment Service emits PaymentConfirmed
Notification Service emits EmailSent
If payment fails: → emit PaymentFailed → Registration Service triggers CancelRegistration → Schedule Service releases seat → Notification Service sends failure email-
4️⃣ Integration Layer
What it is: The bridge between internal microservices and the shared Common Architecture Platform.
Why it matters: It enables seamless interaction between core services and foundational components like notifications, payments, external APIs, data services, and file storage — all while maintaining loose coupling and scalability.
How it works:
Implements the Common Architecture Platform, which includes Notification (Email, SMS, Push), Payment, External Service, Data Service, and File Storage Service
Facilitates communication via message queues and event-driven workflows
Abstracts external dependencies to allow easy replacement or upgrades
Handles retries, fallbacks, and error logging
Ensures consistent integration with the Database Layer through well-defined adapters and service contracts
External Services
Payment Gateway
Processes payments
Stripe API: POST /v1/payment_intents
Email Provider
Sends confirmations
SendGrid API: POST /send
File Storage
Stores admission forms
S3: PUT /admission_123.pdf
Legacy ERP
Syncs student records
JDBC adapter to university DB
5️⃣ Database Layer
What it is: The foundation for storing and retrieving data across services, designed using CQRS and polyglot persistence.
Why it matters: Ensures data consistency, performance, and scalability. By separating read and write models, the system can optimize for both transactional integrity and fast queries.
How it works:
🔹 CQRS (Command Query Responsibility Segregation)
Command DBs handle writes (e.g., registration, payment)
Query DBs serve fast reads (e.g., seat availability, dashboards)
Read models updated asynchronously via events
🔹 Polyglot Persistence
Student Service
PostgreSQL
Redis / Elasticsearch
Relational + Cache
Subject Service
MySQL
MongoDB / Redis
Relational + Document
Schedule Service
PostgreSQL
Redis / Elasticsearch
Relational + Search
Registration Service
PostgreSQL
Redis / Replica
Relational + Cache
Payment Service
Redis
Kafka Streams / Redis
Key-Value + Streaming
Notification Service
DynamoDB
S3 Logs / DynamoDB
NoSQL + Object Storage
Admission Service
Couchbase
S3 / Couch
Document + Object
📄 Case Study 1: Student Profile Creation
How the Student Service interacts across the Microservices Layer, Business Logic Layer (Event-Driven), and Database Layer, using a real-world scenario like student profile creation and update. This will show how data flows, events propagate, and consistency is maintained across layers.
🔄 Student Service: Layer Integration Walkthrough
🧱 Microservices Layer
Role: The Student Service handles CRUD operations for student profiles, including personal details, academic history, and identity verification. Example Operation: A student signs up via the frontend. The UI sends a POST /students request to the Student Service via the API Gateway. What Happens:
The Student Service receives the request
Validates the payload (e.g., name, email, program)
Authenticates the user using JWT
Writes the data into its Command Database (e.g., PostgreSQL)
Emits a domain event: StudentCreated
🧠 Business Logic Layer (Event-Driven Architecture)
Role: Coordinates workflows and propagates domain events to other services. Event Emission: After the student profile is successfully created, the Student Service publishes a StudentCreated event to Kafka or RabbitMQ This event includes metadata like studentId, program, and email Event Consumers:
Notification Service: Listens for StudentCreated → sends welcome email
Analytics Service: Logs the event for reporting
Admission Service: Prepares admission form template
Legacy Sync Adapter: Updates student record in university ERP system Transactional Integrity:
Uses the Transactional Outbox Pattern to ensure the event is only published after the DB commit
If the DB write fails, the event is not emitted
If the event fails to publish, it’s retried via a background worker
🗄️ Database Layer (CQRS + Polyglot Persistence)
Role: Stores and serves data using separate models for commands and queries. 🔹 Command Side
DB: PostgreSQL
Action: Stores full student profile with normalized schema
Use: Write operations like create, update, delete 🔹 Query Side
DB: Redis or Elasticsearch
Action: Stores denormalized, precomputed views for fast access
Use: Read operations like dashboard display, search by name or program 🔹 Read Model Update The StudentCreated event triggers a CDC (Change Data Capture) or event handler Updates the query DB with a materialized view like:
{
"studentId": "S12345",
"name": "Alice Wong",
"program": "BSc Computer Science",
"status": "Active",
"createdAt": "2025-09-04T11:30:00Z"
}🔐 Security Across Layers
Microservices Layer: Validates JWT, enforces RBAC, sanitizes input
Business Layer: Ensures event integrity, prevents spoofing
Database Layer: Encrypts sensitive fields (e.g., email, PII data), applies row-level access control
📄 Case Study 2: Module Registration
This case shows how a student selects and registers for academic modules. The system validates eligibility, checks availability, and confirms scheduling before recording the registration. An event is then emitted to notify services like email, analytics, and scheduling, ensuring reliable and scalable processing through event-driven architecture.
🧩 Microservices & Business Logic Interaction: Module Registration Flow
In a distributed system, microservices often communicate asynchronously to maintain scalability and independence. This page outlines how a module registration request flows through the system — from validation to event emission and consumption — using a robust, event-driven architecture.
Flow Summary
🎯 Scenario: Student Registers for a Module
🔹 Request Payload
{
"studentId": "S12345",
"moduleId": "CS301",
"semester": "Fall 2025"
}🧠 Step 1: Validation via Business Logic Layer
Upon receiving the request, the Microservices Layer delegates to the Business Logic Layer, which orchestrates multiple service calls to validate the module selection.
✅ Validation Step
Student Service
Verify prerequisites and academic standing
Subject Service
Confirm module is offered in the semester
Lecturer Service
Ensure lecturer is assigned and available
Schedule Service
Check if seats are available
Timetable Service
Avoid clashes with existing student schedule
If any check fails, the process halts and returns an error. If all pass, the system proceeds to the next step.
🧾 Step 2: Transactional Write + Outbox Update
The Business Logic Layer performs a single atomic transaction:
Insert registration record into the Command DB
Insert domain event into the Outbox Table:
{
"eventType": "ModuleRegistered",
"studentId": "S12345",
"moduleId": "CS301",
"semester": "Fall 2025",
"timestamp": "2025-09-04T11:45:00Z"
}This ensures that the event is only emitted if the registration was successfully recorded.
📤 Step 3: Event Queued by Outbox Processor
A background worker scans the Outbox Table and publishes new events to a message broker (e.g., Kafka, RabbitMQ):
Topic: module-registration-events
Status: Event marked as “dispatched” after successful publish
This decouples event emission from the main request flow and guarantees reliability.
📬 Step 4: Event Consumption by Subscribers
Multiple services subscribe to the event topic and react independently:
Notification Service
Sends confirmation email to student
Analytics Service
Logs registration event for reporting
Admission Service
Updates academic plan
Schedule Service
Decrements seat count
Each consumer deserializes the event and executes its own logic, enabling parallel and resilient processing.
🔁 Optional: Chained Events Some consumers may emit follow-up events:
Schedule Service → emits SeatUpdated
Admission Service → emits AdmissionUpdated
These trigger further reactions, forming a reactive event chain.
✅ Benefits of This Architecture
Atomicity: Ensures DB write and event emission are tightly coupled
Scalability: Consumers process events independently
Resilience: Failed consumers can retry without affecting others
Traceability: Outbox table provides audit trail for emitted events
Loose Coupling: Services evolve independently without tight integration
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