Cloud-Native SaaS Multi-Tenant Architecture

Architecture-level multi-tenant SaaS platform demonstrating tenant isolation, RBAC, event-driven workflows, Redis caching, RabbitMQ messaging, PostgreSQL database design, audit logging, retries, dead-letter queues, and cloud-native scalability.

This repository is designed as a system design and software architecture showcase.

Problem Statement

Modern SaaS platforms serve multiple organizations using the same application while ensuring security, tenant isolation, scalability, and operational reliability.

This project explains how to design a production-grade multi-tenant SaaS platform where multiple companies can use the same system without data leakage, noisy-neighbor issues, or inconsistent authorization.

Core Features

• Multi-tenant SaaS architecture
• Tenant onboarding workflow
• Tenant isolation strategy
• Role-Based Access Control
• API Gateway pattern
• Event-driven microservices
• RabbitMQ messaging
• Retry and dead-letter queue strategy
• Redis caching
• PostgreSQL database design
• Audit logging
• Notification workflows
• Billing/subscription workflow
• Rate limiting per tenant
• Security considerations
• Horizontal scaling strategy
• Docker-based local infrastructure

Core Services

Service	Responsibility
API Gateway	Entry point, routing, authentication, rate limiting
Tenant Service	Tenant lifecycle, tenant settings, domains
Auth Service	Login, JWT/OAuth, identity management
RBAC Service	Roles, permissions, access control
Billing Service	Subscriptions, invoices, payment events
Audit Service	Immutable audit trail
Notification Service	Email/SMS/push notifications

High-Level Architecture

flowchart TD
    Client[Client / Web App] --> Gateway[API Gateway]
    Gateway --> Auth[Auth Service]
    Gateway --> Tenant[Tenant Service]
    Gateway --> RBAC[RBAC Service]
    Gateway --> Billing[Billing Service]
    Auth --> DB[(PostgreSQL)]
    Tenant --> DB
    RBAC --> DB
    Billing --> DB
    Gateway --> Redis[(Redis Cache)]
    Tenant --> MQ[RabbitMQ Event Bus]
    Billing --> MQ
    Auth --> MQ
    MQ --> Audit[Audit Service]
    MQ --> Notification[Notification Service]
    Audit --> AuditDB[(Audit Logs DB)]
    Notification --> Provider[Email / SMS Provider]

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Documentation

Document	Description
Problem Statement	Business and technical problem
Requirements	Functional and non-functional requirements
High-Level Architecture	Main system architecture
Multi-Tenancy Strategy	Shared DB, schema, isolated DB options
RBAC Design	Roles, permissions, authorization flow
Event-Driven Workflow	RabbitMQ-based async communication
Database Design	Core tables and tenant-aware schema
Scaling Strategy	Horizontal scaling, caching, queues
Security Considerations	Tenant security, JWT, audit, encryption
Failure Handling	Retry, DLQ, idempotency, circuit breakers

Technical Deep Dives

This architecture is also documented in detail on:

• Hashnode Technical Deep Dive: https://rummansystems.hashnode.dev/designing-a-cloud-native-multi-tenant-saas-architecture-with-node-js-rabbitmq-redis-and-postgresql

• Medium Architecture Case Study: https://medium.com/@rummansiddiqui1990/designing-a-cloud-native-multi-tenant-saas-architecture-with-node-js-and-rabbitmq-bc6ac5546020

Diagrams

Diagram	File
High-Level Architecture	diagrams/high-level-architecture.md
Tenant Onboarding Flow	diagrams/tenant-onboarding-flow.md
RBAC Authorization Flow	diagrams/rbac-flow.md
Event-Driven Flow	diagrams/event-driven-flow.md
Retry + DLQ Flow	diagrams/retry-dlq-flow.md

Tech Stack

• Node.js
• NestJS
• PostgreSQL
• Redis
• RabbitMQ
• Docker
• Nginx
• JWT/OAuth
• GitHub Actions
• AWS-ready cloud design

Local Infrastructure Setup

docker compose up -d

RabbitMQ Management UI:

http://localhost:15672
Username: guest
Password: guest

Example Event Names

tenant.created
tenant.updated
user.invited
subscription.created
payment.completed
payment.failed
notification.requested
audit.log.created

Future Improvements

• Add actual NestJS implementations
• Add Kubernetes manifests
• Add Terraform infrastructure
• Add OpenTelemetry tracing
• Add Prometheus/Grafana monitoring
• Add automated architecture tests
• Add database migration examples
• Add CI/CD pipeline

Repository Purpose

This repository demonstrates architecture-level thinking around distributed systems, SaaS platforms, microservices, tenant isolation, and cloud-native engineering.

License

This repository is licensed under the MIT License.