50_1: Introduction

A 3-tier architecture is a structured design pattern that separates an application into three distinct layers:

1️⃣ Presentation Layer (Web Tier) – Manages user interface and interactions.

2️⃣ Application Layer (Logic Tier) – Processes business logic and request handling.

3️⃣ Data Layer (Database Tier) – Stores and manages application data.

This architecture promotes modularity, scalability, and security, making it an industry-standard approach for cloud-based applications.

50_2: Understanding the Three Tiers in OCI

1. Presentation Layer (Web Tier)

   • Function: Handles user interactions and displays content.

   • OCI Services Used:

   • OCI Load Balancer → Distributes incoming requests to backend servers.

   • Compute Instances → Runs web server applications (e.g., Apache, Nginx).

2. Application Layer (Logic Tier)

   • Function: Processes requests, executes business logic, and communicates between the frontend and database.

   • OCI Services Used:

   • Compute Instances → Hosts backend services (e.g., Java, Node.js, Python).

   • OCI Container Engine for Kubernetes (OKE) → For containerized deployments.

3. Data Layer (Database Tier)

   • Function: Stores and manages structured and unstructured data.

   • OCI Services Used:

   • OCI Autonomous Database → Fully managed database for minimal maintenance .

   • OCI MySQL, PostgreSQL, Oracle Database → For custom database solutions.

   • OCI Object Storage → Stores unstructured data (e.g., logs, media files).

50_3: 3-Tier Architecture Design in OCI

                 ┌──────────────────────────────┐
                 │         Internet             │
                 └──────────────▲──────────────┘
                                │
                 ┌──────────────▼──────────────┐
                 │      OCI Load Balancer      │  (Public Subnet)
                 └──────────────▲──────────────┘
                                │
            ┌───────────────────┴───────────────────┐
            │                                       │
  ┌────────▼────────┐                     ┌────────▼────────┐
  │  Web Server 1   │                     │  Web Server 2   │  (Public Subnet)
  └────────────────┘                     └────────────────┘
            │                                       │
            └───────────────┬───────────────┘
                            │
                ┌───────────▼───────────┐
                │  Application Servers  │  (Private Subnet)
                └───────────▲───────────┘
                            │
                ┌───────────▼───────────┐
                │  Oracle Database      │  (Private Subnet)
                └───────────────────────┘

This model ensures secure communication between layers while isolating backend resources from direct internet access.

50_4: Steps to Deploy a 3-Tier Architecture in OCI

• Step 1: Create a Virtual Cloud Network (VCN) and Subnets

  1. Set up a VCN with a CIDR block (e.g., 10.0.0.0/16).
  2. Define three subnets: Public Subnet → For the load balancer and web servers (10.0.1.0/24). Private Subnet → For application servers (10.0.2.0/24). Private Subnet → For the database server (10.0.3.0/24).

• Step 2: Deploy the Web Tier

  1. Launch OCI Load Balancer in the public subnet.
  2. Deploy Compute Instances in the public subnet to host web servers.
  3. Install a web server (e.g., Apache, Nginx) on the instances.
  4. Configure security lists to allow HTTP(S) traffic from the internet.

• Step 3: Deploy the Application Tier

  1. Deploy Compute Instances in a private subnet.
  2. Install backend frameworks (e.g., Node.js, Java Spring Boot, Python Flask).
  3. Configure security rules to allow traffic only from the web tier.

• Step 4: Deploy the Database Tier

  1. Launch an OCI Autonomous Database or Oracle Database in a private subnet.
  2. Configure Network Security Groups (NSG) to restrict access.
  3. Allow database connections only from the application servers.

• Step 5: Configure Security & Networking

  1. Set up security lists for controlled communication: Web Tier → App Tier (Allow HTTP/HTTPS traffic). App Tier → Database Tier (Allow DB connections).
  2. Define route tables to manage data flow between subnets.

• Step 6: Enable Scaling & Load Balancing

  1. Enable Auto-Scaling for web and application servers.
  2. Configure the OCI Load Balancer to distribute traffic efficiently.

• Step 7: Deploy & Test the Application

  1. Deploy application code on application servers.
  2. Validate end-to-end communication across all layers.

50_5: Why Use a 3-Tier Architecture in OCI?

✅ Improved Security → Private subnets prevent direct database exposure.

✅ Better Scalability → Each layer scales independently based on demand.

✅ High Availability → Load balancers ensure seamless traffic management.

✅ Simplified Maintenance → Modular design allows easier updates and troubleshooting.

By implementing this structure, you can enhance performance, security, and flexibility for cloud applications in Oracle Cloud Infrastructure (OCI). 🚀