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Links: 101 AWS SAA Index

  • Managed database service SQL databases.
  • List of database engines (6 = 5 + 1) which are managed by AWS (Postgres, Maria, Oracle, MySQL, Ms SQL server) and the last is Aurora which is AWS proprietary.

Why use RDS instead of manually provisioning databases on EC2

  • Automated provisioning and OS patching
  • RDS Read Replica to improve read performance.
  • RDS Multi AZ setup for disaster recovery.
  • To handle a higher load in your database, you can vertically scale up your master database with a simple push of a button.
  • In addition to scaling your master database vertically, you can also improve the performance of a read-heavy database by using read replicas to horizontally scale your database.
  • You can restore a DB instance to a specific point in time, creating a new DB instance.
You cannot SSH into RDS instances.

Automated Backups

  • We get automated backups in RDS. Features of Automated backups.

    • Daily full backup of the database (during the maintenance window)
    • Transaction logs are backed-up by RDS every 5 minutes.
    • Ability to restore to any point in time (from oldest backup to 5 minutes ago)
      • When you do a point in time restore the default SG is applied to the new database.
    • 7 days retention (can be increased to 35 days)
  • Backups which are manually triggered by the user are known as snapshots.

  • Snapshots can be retained as long as we want. In automated backups its 7 days by default and maximum of 35 days.
Backups are stored in S3.

Just for reference, snapshots of EBS volumes were also stored in S3.


  • RDS will detect when you are running out of space and will scale automatically with zero downtime. This means we don’t have to scale our database manually.
  • We set a desired maximum(since we don't want to scale our DB infinitely) and auto scaling takes care of the rest.
Autoscaling will only work if it is enabled. It is disabled by default.

If you are running into storage issues make sure that autoscaling is enabled for a simple and easy fix.

  • There is no additional charge for autoscaling.
  • It is supported by all database engines.
Whenever you see RDS instance is running out of storage always go for auto scaling for increasing the disk space instead of manually increasing the disk space in instance settings.

Keywords like minimum development and database administration maybe mentioned.

RDS Monitoring

  • Amazon RDS provides metrics in real time for the operating system (OS) that your DB instance runs on. This is known as enhanced monitoring.
  • You can view the metrics for your DB instance using the console(I think CloudWatch console), or consume the Enhanced Monitoring JSON output from CloudWatch Logs in a monitoring system of your choice
How does CloudWatch metrics and Enhanced Monitoring differ from each other in case of RDS monitoring?
  • CloudWatch gathers metrics about CPU utilisation from the hypervisor for a DB instance,
  • Enhanced Monitoring gathers its metrics from an agent on the instance.

  • As a result, you might find differences between the measurements, because the hypervisor layer performs a small amount of work. The differences can be greater if your DB instances use smaller instance classes, because then there are likely more virtual machines (VMs) that are managed by the hypervisor layer on a single physical instance.
  • Data provided by CloudWatch is not as detailed as RDS Enhanced Monitoring.
  • Since we do not have access to the EC2 instances running our database we cannot install CloudWatch agents or custom scripts for specific parameters. We are dependent on Enhanced monitoring.
  • Enhanced Monitoring metrics are useful when you want to see how different processes or threads on a DB instance use the CPU.
  • We can view the following in enhanced monitoring: RDS child processes, RDS processes, OS processes.
Whenever you see processes and threads in question go for RDS Enhanced monitoring.

Last updated: 2022-05-05