rds

# AWS RDS

Amazon Relational Database Service (RDS) provides managed relational databases including MySQL, PostgreSQL, MariaDB, Oracle, SQL Server, and Aurora. RDS handles provisioning, patching, backups, and failover.

## Table of Contents

- [Core Concepts](#core-concepts)
- [Common Patterns](#common-patterns)
- [CLI Reference](#cli-reference)
- [Best Practices](#best-practices)
- [Troubleshooting](#troubleshooting)
- [References](#references)

## Core Concepts

### DB Instance Classes

| Category | Example | Use Case |
|----------|---------|----------|
| Standard | db.m6g.large | General purpose |
| Memory Optimized | db.r6g.large | High memory workloads |
| Burstable | db.t3.medium | Variable workloads, dev/test |

### Storage Types

| Type | IOPS | Use Case |
|------|------|----------|
| gp3 | 3,000-16,000 | Most workloads |
| io1/io2 | Up to 256,000 | High-performance OLTP |
| magnetic | N/A | Legacy, avoid |

### Multi-AZ Deployments

- **Multi-AZ Instance**: Synchronous standby in different AZ
- **Multi-AZ Cluster**: One writer, two reader instances (Aurora-like)

### Read Replicas

Asynchronous copies for read scaling. Can be cross-region.

## Common Patterns

### Create a PostgreSQL Instance

**AWS CLI:**

```bash
# Create DB subnet group
aws rds create-db-subnet-group \
  --db-subnet-group-name my-db-subnet-group \
  --db-subnet-group-description "Private subnets for RDS" \
  --subnet-ids subnet-12345678 subnet-87654321

# Create security group (allow PostgreSQL from app)
aws ec2 create-security-group \
  --group-name rds-postgres-sg \
  --description "RDS PostgreSQL access" \
  --vpc-id vpc-12345678

aws ec2 authorize-security-group-ingress \
  --group-id sg-rds12345 \
  --protocol tcp \
  --port 5432 \
  --source-group sg-app12345

# Create RDS instance
aws rds create-db-instance \
  --db-instance-identifier my-postgres \
  --db-instance-class db.t3.medium \
  --engine postgres \
  --engine-version 16.1 \
  --master-username admin \
  --master-user-pass