Intro

• Regional Service
• Supports Multi AZ
• AWS Managed SQL Database
• Supported Engines
  • Postgres
  • MySQL
  • MariaDB
  • Oracle
  • Microsoft SQL Server
  • Aurora (AWS Proprietary database)
• Backed by EC2 instances with EBS storage
• We don't have access to the underlying instance (cannot SSH into it)
• DB connection is made on port 3306
• SG is used for network security (must allow incoming TCP traffic on port 3306 from specific IPs)

Backups

• Automated Backups (enabled by default)
  • Daily full backup of the database (during the defined maintenance window)
  • Backup retention: 7 days (max 35 days)
  • Transaction logs are backed-up every 5 minutes for Point In Time Recovery (PITR)
  • Automated backups happen in the same region (can happen in multiple AZs in a multi-AZ deployment)
• DB Snapshots:
  • Manually triggered
  • Backup retention: unlimited
  • Snapshots can be saved across regions

Auto Scaling

• Automatically scales the RDS storage within the max limit
• Condition for automatic storage scaling:
  • Free storage is less than 10% of allocated storage
  • Low-storage lasts at least 5 minutes
  • 6 hours have passed since last modification

Read Replicas

• Allows us to scale the read operation (SELECT) on RDS
• Up to 5 read replicas (within AZ, cross AZ or cross region)
• Asynchronous Replication (seconds)
• Replicas can be promoted to their own DB
• Applications must update the connection string to leverage read replicas

• Network fee for replication
  • Same region: free
  • Cross region: paid