Understanding SaaS Architecture: Cloud Service Models, Multi‑Tenant Design, and Core Components

This article introduces the fundamentals of SaaS systems, covering cloud service models, key characteristics, classification, and multi‑tenant architecture.

1. Cloud Service Architecture Concepts

PaaS (Platform‑as‑a‑Service) provides a development platform where customers deploy applications without managing underlying infrastructure.

IaaS (Infrastructure‑as‑a‑Service) offers raw compute, storage, and networking resources that users can configure and run any software on.

SaaS (Software‑as‑a‑Service) delivers complete applications hosted on the cloud, accessed via browsers or client apps.

2. Two Main Features of SaaS

• Hosted on the provider’s servers rather than the customer’s premises.

• Subscription‑based model with modular functionality and pay‑per‑usage pricing.

3. SaaS vs. Traditional vs. Internet Services

SaaS sits between traditional on‑premise software and pure internet services, offering rented, cloud‑deployed applications with shared maintenance.

4. B2B2C Model

SaaS platforms must serve both end‑users (C‑side) and business operators (B‑side) with features like tenant management, traffic monitoring, and operational dashboards.

5. SaaS Classification

Business‑type SaaS : Tools that directly support revenue‑generating activities (e.g., e‑commerce, CRM).

Efficiency‑type SaaS : Productivity tools that improve internal processes (e.g., project management, video conferencing).

Hybrid SaaS : Combines business and efficiency functions in a single solution.

6. How to SaaSify an Application

Key steps include cloud deployment, user‑system redesign for 2C login, gateway services (rate limiting, anti‑tamper), tenant management, web‑frontend adaptation, website for quoting and payment, and data‑level permission redesign.

7. Core Components of a SaaS Product

Security, data isolation, configurability, extensibility, zero‑downtime upgrades, and multi‑tenant support are essential building blocks.

8. Multi‑Tenant Architecture

Key concepts: tenant, user, organization, employee, solution, product capability, resource domain, and cloud resources.

Three isolation models:

• Vertical (well‑bore) isolation : Each tenant runs in a completely separate environment, offering strong isolation but higher cost and management complexity.

• Shared model : Tenants share the same infrastructure, enabling efficient resource use and easier management, but requiring careful throttling to avoid tenant impact.

• Domain‑segmented model : Combines aspects of both, isolating domains while sharing underlying resources.

Required capabilities include shared/cloud resource usage, strict data and behavior isolation, organization‑based management, and flexible deployment of product capabilities across resources.