Platform System Overview - Production-Ready Architecture Sequence Diagrams

Scenario 1: Multi-Tenant System Initialization & Health Check

Triggering Event: Platform starts up and performs comprehensive health validation

sequenceDiagram
    participant DevOps as Platform Engineer
    participant Docker as Docker Container
    participant Backend as API Server
    participant Database as PostgreSQL
    participant Redis as Redis Cache
    participant S3 as AWS S3
    participant Monitoring as Prometheus
    participant LoadBalancer as Nginx
    participant Security as WAF
    
    DevOps->>Docker: docker-compose up -d
    Docker->>Backend: Start API server container
    Docker->>Database: Start PostgreSQL container
    Docker->>Redis: Start Redis container
    Docker->>LoadBalancer: Start Nginx container
    Docker->>Monitoring: Start Prometheus container
    
    Backend->>Backend: Initialize application modules
    Backend->>Database: Test database connection
    Database-->>Backend: Connection successful
    Backend->>Database: Run migration scripts
    Database->>Database: Apply schema changes
    Database-->>Backend: Migration completed
    
    Backend->>Redis: Test Redis connection
    Redis-->>Backend: Connection successful
    Backend->>Redis: Warm cache with frequently accessed data
    Redis-->>Backend: Cache warmed
    
    Backend->>S3: Test AWS S3 connectivity
    S3-->>Backend: Connection verified
    Backend->>S3: Verify bucket permissions
    S3-->>Backend: Permissions confirmed
    
    Backend->>LoadBalancer: Register with load balancer
    LoadBalancer->>Security: Configure Web Application Firewall
    Security-->>LoadBalancer: Security rules applied
    LoadBalancer-->>Backend: Ready to receive traffic
    
    Backend->>Monitoring: Register metrics endpoints
    Monitoring-->>Backend: Metrics collection started
    Backend->>Monitoring: Register health check endpoint
    Monitoring-->>Backend: Health monitoring active
    
    Backend->>Backend: Start background job processors
    Backend->>Backend: Initialize WebSocket server
    Backend->>Backend: Start scheduled tasks (cron jobs)
    
    Backend->>DevOps: Platform health check completed
    DevOps->>DevOps: Verify all services operational
    DevOps->>Monitoring: Check system metrics
    Monitoring-->>DevOps: All systems green

Scenario 2: Cross-Microservice User Authentication Flow

Triggering Event: User attempts login with multi-service validation

sequenceDiagram
    participant User as Any User
    participant CDN as CloudFlare
    participant LoadBalancer as Nginx
    participant API as API Gateway
    participant AuthService as Auth Service
    participant UserDB as User Database
    participant Redis as Redis Cache
    participant Audit as Audit Service
    participant Monitoring as Prometheus
    participant Analytics as Analytics Service
    
    User->>CDN: GET https://ku-connect.com/login
    CDN->>CDN: Check for cached login page
    CDN-->>User: Serve cached login page
    
    User->>CDN: POST login form (email, password)
    CDN->>LoadBalancer: Forward to API gateway
    LoadBalancer->>API: Authenticate request
    
    API->>API: Rate limiting check (IP/user based)
    API->>API: Validate CSRF token
    API->>API: Check request signature
    API->>AuthService: POST /auth/login
    
    AuthService->>AuthService: Validate input format
    AuthService->>Redis: Check failed login attempts
    Redis-->>AuthService: Failed attempts: 2/5 (within 15 min)
    
    AuthService->>UserDB: SELECT User WHERE email = ?
    UserDB->>UserDB: Check account status (locked/active)
    UserDB-->>AuthService: User found, account active
    
    AuthService->>AuthService: Compare password hash
    AuthService->>AuthService: Generate session ID
    AuthService->>Redis: Store session with TTL (24h)
    Redis-->>AuthService: Session stored
    AuthService->>Redis: Clear failed login counter
    Redis-->>AuthService: Counter cleared
    
    AuthService->>UserDB: UPDATE User SET lastLogin = ?, loginCount = loginCount + 1
    UserDB-->>AuthService: Login record updated
    
    AuthService->>Audit: Log authentication event
    Audit->>Audit: Record IP, timestamp, user agent
    Audit->>Monitoring: Update login metrics
    Monitoring-->>AuthService: Metrics updated
    
    AuthService->>Analytics: Track login patterns
    Analytics->>Analytics: Update user activity analytics
    
    AuthService->>API: Return JWT access_token + refresh_token
    API->>API: Apply response security headers
    API->>LoadBalancer: Forward authenticated response
    LoadBalancer->>CDN: Return to user
    CDN-->>User: 200 OK + authentication tokens + dashboard redirect
    
    Note over AuthService, Analytics: Asynchronous post-login processes
    AuthService->>AuthService: Trigger user preference loading
    AuthService->>Analytics: Update login geography data
    AuthService->>Monitoring: Update concurrent user count
    Analytics->>Analytics: Generate login behavior insights

Scenario 3: Real-Time Distributed Data Synchronization

Triggering Event: Student applies for job triggering multi-system updates

sequenceDiagram
    participant Student as CPE Student
    participant Frontend as React App
    participant API as API Gateway
    participant JobService as Job Service
    participant ApplicationService as Application Service
    participant NotificationService as Notification Service
    participant SearchService as Elasticsearch
    participant Cache as Redis Cluster
    participant Database as PostgreSQL Cluster
    participant Queue as RabbitMQ
    participant Analytics as Analytics Service
    participant Company as HR Manager
    
    Student->>Frontend: Click "Apply" on Software Engineer job
    Frontend->>API: POST /api/applications (with JWT)
    
    API->>API: Validate JWT and rate limits
    API->>API: Request routing to Application Service
    API->>ApplicationService: Create application request
    
    ApplicationService->>ApplicationService: Validate application data
    ApplicationService->>Database: Check for duplicate application
    Database-->>ApplicationService: No duplicate found
    
    ApplicationService->>Database: BEGIN TRANSACTION
    ApplicationService->>Database: INSERT Application (status: PENDING)
    Database-->>ApplicationService: Application created
    ApplicationService->>Database: INSERT ApplicationHistory (status change)
    Database-->>ApplicationService: History logged
    ApplicationService->>Database: COMMIT TRANSACTION
    
    ApplicationService->>Queue: Publish application_created event
    ApplicationService->>Cache: Update application cache
    Cache-->>ApplicationService: Cache updated
    
    ApplicationService->>SearchService: Index new application
    SearchService->>SearchService: Update search index
    SearchService-->>ApplicationService: Index updated
    
    ApplicationService->>API: Return application ID
    API->>Frontend: 201 Created + application details
    Frontend->>Student: Show application confirmation
    
    Note over Queue, Analytics: Asynchronous event processing
    Queue->>NotificationService: Consume application_created event
    NotificationService->>NotificationService: Generate notification templates
    NotificationService->>Company: Send "New Application" email
    NotificationService->>Student: Send "Application Confirmation" email
    NotificationService->>Queue: Publish notification_sent events
    
    Queue->>Analytics: Consume application_created event
    Analytics->>Analytics: Update application metrics
    Analytics->>Analytics: Calculate real-time funnel data
    Analytics->>Analytics: Update job application trends
    
    Queue->>JobService: Consume application_created event
    JobService->>JobService: Update job application count
    JobService->>Database: UPDATE Job SET applicationCount = applicationCount + 1
    JobService->>Cache: Update job cache
    JobService->>Queue: Publish job_updated event
    
    Note over Company, Student: Real-time updates
    Company->>Frontend: Receive WebSocket notification
    Frontend->>Company: Show "New application received" toast
    Company->>Frontend: Click to review application
    
    Student->>Frontend: Receive WebSocket update
    Frontend->>Student: Update application status to "Submitted"

Scenario 4: High-Availability Failover & Disaster Recovery

Triggering Event: Primary database fails triggering automatic failover

sequenceDiagram
    participant User as Active User
    participant LoadBalancer as Load Balancer
    participant API as API Gateway
    participant PrimaryDB as Primary PostgreSQL
    participant SecondaryDB as Secondary PostgreSQL
    participant Monitor as Health Monitor
    participant AlertManager as Alert Manager
    participant DevOps as Platform Engineer
    participant Cache as Redis Cluster
    participant Queue as Message Queue
    participant Backup as S3 Backup
    
    PrimaryDB->>Monitor: Health check failure
    Monitor->>Monitor: Confirm database unresponsiveness
    Monitor->>AlertManager: Trigger critical alert
    
    AlertManager->>DevOps: SMS/Email: Primary database down!
    AlertManager->>AlertManager: Runbook: Database failover procedure
    
    LoadBalancer->>API: Continue routing requests
    API->>PrimaryDB: Attempt database query
    PrimaryDB-->>API: Connection timeout
    
    API->>Monitor: Report database failure
    Monitor->>API: Initiate automatic failover
    API->>SecondaryDB: Switch to secondary database
    SecondaryDB-->>API: Promotion to primary successful
    
    SecondaryDB->>SecondaryDB: Begin recovery process
    SecondaryDB->>Backup: Verify last backup integrity
    Backup-->>SecondaryDB: Backup verified
    SecondaryDB->>Backup: Replay transaction logs
    Backup-->>SecondaryDB: Recovery complete
    
    API->>Cache: Update database connection strings
    Cache-->>API: Connection cache updated
    API->>Queue: Pause message processing
    Queue-->>API: Processing paused
    
    DevOps->>Monitor: Check system status
    Monitor-->>DevOps: Failover complete, systems stable
    DevOps->>SecondaryDB: Verify data consistency
    SecondaryDB-->>DevOps: Data integrity confirmed
    
    LoadBalancer->>API: Resume full traffic
    API->>SecondaryDB: Resume normal operations
    SecondaryDB-->>API: All queries successful
    
    Queue->>Queue: Resume message processing
    Queue->>API: Process queued requests
    API->>SecondaryDB: Handle backlog
    SecondaryDB-->>Queue: Backlog cleared
    
    Note over DevOps, Backup: Recovery procedure
    DevOps->>PrimaryDB: Diagnose original failure
    DevOps->>PrimaryDB: Fix underlying issue
    DevOps->>PrimaryDB: Rebuild as secondary
    PrimaryDB->>SecondaryDB: Synchronize from current primary
    SecondaryDB-->>PrimaryDB: Synchronization complete
    
    DevOps->>Monitor: Update monitoring configurations
    Monitor-->>DevOps: All systems operational
    DevOps->>AlertManager: Clear critical alerts
    AlertManager->>DevOps: Recovery confirmed

Scenario 5: Microservice Orchestration for Complex Business Workflows

Triggering Event: Company submits bulk hiring request triggering orchestration

sequenceDiagram
    participant HR as HR Manager
    participant Frontend as React App
    participant API as API Gateway
    participant Orchestrator as Workflow Orchestrator
    participant ValidationService as Validation Service
    participant CompanyService as Company Service
    participant JobService as Job Service
    participant MatchingService as AI Matching Service
    participant Queue as RabbitMQ
    participant PaymentService as Payment Service
    participant ComplianceService as Compliance Service
    participant NotificationService as Notification Service
    participant AuditService as Audit Service
    participant Analytics as Analytics Service
    participant University as University Admin
    
    HR->>Frontend: Submit bulk hiring request (50 positions)
    Frontend->>API: POST /api/company/bulk-hiring (with JWT)
    API->>Orchestrator: Initiate bulk hiring workflow
    
    Orchestrator->>ValidationService: Validate bulk request data
    ValidationService->>ValidationService: Check business rules and limits
    ValidationService->>CompanyService: Verify company subscription
    CompanyService->>CompanyService: Check credit limits and pricing
    CompanyService-->>ValidationService: Subscription verified
    ValidationService-->>Orchestrator: Validation passed
    
    Orchestrator->>PaymentService: Process bulk posting fee
    PaymentService->>PaymentService: Calculate pricing (50 positions)
    PaymentService->>PaymentService: Process payment via Stripe
    PaymentService-->>Orchestrator: Payment successful
    
    Orchestrator->>Queue: Publish bulk_job_creation task
    Queue->>JobService: Process bulk job creation
    loop Create 50 job postings
        JobService->>JobService: Create individual job posting
        JobService->>JobService: Validate job requirements
        JobService->>Queue: Publish job_created event
    end
    
    Queue->>MatchingService: Process job matching for each job
    loop Process 50 jobs
        MatchingService->>MatchingService: Find matching students
        MatchingService->>MatchingService: Calculate match scores
        MatchingService->>Queue: Publish matches_found event
    end
    
    Queue->>ComplianceService: Review bulk posting compliance
    ComplianceService->>ComplianceService: Check university policies
    ComplianceService->>ComplianceService: Verify equal opportunity compliance
    ComplianceService->>University: Notify of bulk hiring activity
    University-->>ComplianceService: Compliance approved
    
    Queue->>NotificationService: Send notifications
    NotificationService->>NotificationService: Prepare targeted notifications
    NotificationService->>NotificationService: Batch email to matched students
    NotificationService->>NotificationService: Send confirmation to HR
    NotificationService-->>Orchestrator: Notifications sent
    
    Queue->>AnalyticsService: Process bulk hiring analytics
    AnalyticsService->>AnalyticsService: Update hiring funnel metrics
    AnalyticsService->>AnalyticsService: Calculate impact on student applications
    AnalyticsService->>AnalyticsService: Generate university partnership value
    
    Queue->>AuditService: Complete audit trail
    AuditService->>AuditService: Log all workflow steps
    AuditService->>AuditService: Store compliance documentation
    AuditService->>AuditService: Create audit report
    
    Orchestrator->>Orchestrator: Complete workflow
    Orchestrator->>API: Return bulk posting results
    API->>Frontend: 200 OK + bulk posting summary
    Frontend->>HR: Show "50 jobs posted, 2,500 students notified"
    
    Note over HR, University: Ongoing monitoring
    HR->>Frontend: Monitor application progress
    Frontend->>API: GET /api/company/bulk-progress (with JWT)
    API->>AnalyticsService: Get real-time bulk hiring metrics
    AnalyticsService-->>API: Progress data
    API-->>Frontend: Current application statistics
    Frontend->>HR: Show live dashboard of applications

Key Production Architecture Features:

1. High Availability & Resilience

• Multi-region deployment with automatic failover
• Database clustering with primary/replica setup
• Load balancing with health checks
• Circuit breakers and retry mechanisms
• Graceful degradation for partial outages

2. Microservices Architecture

• Service discovery and registration
• Inter-service communication via message queues
• API gateway for request routing and aggregation
• Distributed tracing and monitoring
• Service mesh for secure communication

3. Security & Compliance

• Zero-trust security model
• End-to-end encryption
• Comprehensive audit logging
• GDPR and data privacy compliance
• WAF protection and DDoS mitigation

4. Scalability & Performance

• Horizontal scaling with container orchestration
• Caching at multiple levels (CDN, Redis, Application)
• Asynchronous processing for heavy workloads
• Database sharding and connection pooling
• CDN integration for static assets

5. Observability & Monitoring

• Real-time metrics collection (Prometheus)
• Distributed tracing (Jaeger)
• Centralized logging (ELK Stack)
• Application performance monitoring
• Business intelligence dashboards

6. Enterprise Integration

• SAML/OAuth2 for university SSO
• Message queue orchestration for complex workflows
• Event-driven architecture for real-time updates
• Third-party service integrations (payment, email, storage)
• API rate limiting and quota management

7. Data Management

• Multi-database strategy (PostgreSQL, Redis, Elasticsearch)
• Data replication and backup strategies
• Data governance and lineage tracking
• Real-time data synchronization
• Archive and retention policies