17. RDS

RDS (Relational Database Service)

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Prerequisites

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1. RDS

Amazon RDS is a managed relational database service that allows you to run databases without managing infrastructure.

AWS automatically handles:

• OS patching
• Backup
• Failover
• Monitoring

1-1. Supported Engines

• MySQL
• PostgreSQL
• MariaDB
• Oracle
• SQL Server
• Amazon Aurora

1-2. Architecture (with EC2)

User
→ ALB
→ EC2 (Application Server)
→ RDS (Database)

👉 Users do NOT access RDS directly 👉 Only EC2 communicates with RDS

1-3. Network Placement

Public Subnet:
- ALB

Private Subnet:
- EC2
- RDS

👉 RDS must be placed in a Private Subnet

1-4. Performance Factors

• Instance size (CPU / RAM)
• Storage IOPS
• Number of connections
• Query complexity

2. How to work RDS

Component	Role
RDS	Managed database
Endpoint	Database access point
Security Group	Access control
Multi-AZ	High availability
Read Replica	Read scaling

2-1. Connectivity Flow

Application → Database

EC2 → RDS Endpoint

Example:

mydb.abc123.ap-southeast-2.rds.amazonaws.com:3306

Protocol

• MySQL → TCP 3306
• PostgreSQL → TCP 5432

2-2. Routing (VPC Internal)

10.0.0.0/16 → local

👉 Communication stays inside VPC

2-3. Security

RDS Security Group

Inbound:
Port: 3306
Source: EC2 Security Group

Outbound:
Allow all (default)

EC2 → RDS ✅
Internet → RDS ❌

2-4. Multi-AZ

Single AZ

EC2 → RDS (Primary)

Multi-AZ

Primary DB (AZ1)
↓ replication
Standby DB (AZ2)

Failover

Primary failure
→ Automatic switch to standby

3. How to create RDS

3-1. Search RDS

3-2. Click Navigation pane → “Dashboard”

3-3. Click Button → “Create”

3-4. Create database

3-5. Connect EC2

3-6. Check Connection steps on EC2

3-7. Connect RDS’s SQL on EC2

3-8. Command SQL on EC2