AWS Relational Database Service – RDS

Relational Database Service – RDS

  • Relational Database Service – RDS is a web service that makes it easier to set up, operate, and scale a relational database in the cloud.
  • provides cost-efficient, resizable capacity for an industry-standard relational database and manages common database administration tasks such as hardware provisioning, database setup, patching, and backups.
  • features & benefits
    • CPU, memory, storage, and IOPs can be scaled independently.
    • manages backups, software patching, automatic failure detection, and recovery.
    • automated backups can be performed as needed, or manual backups can be triggered as well. Backups can be used to restore a database, and the restore process works reliably and efficiently.
    • provides Multi-AZ high availability with a primary instance and a synchronous standby secondary instance that can failover seamlessly when a problem occurs.
    • provides elasticity & scalability by enabling Read Replicas to increase read scaling.
    • supports MySQL, MariaDB, PostgreSQL, Oracle, and Microsoft SQL Server, and the new, MySQL-compatible Aurora DB engine
    • supports IAM users and permissions to control who has access to the RDS database service
    • databases can be further protected by putting them in a VPC, using SSL for data in transit and encryption for data in rest
    • However, as it is a managed service, shell (root ssh) access to DB instances is not provided, and this restricts access to certain system procedures and tables that require advanced privileges.

RDS Components

  • DB Instance
    • is a basic building block of RDS
    • is an isolated database environment in the cloud
    • each DB instance runs a DB engine. AWS currently supports MySQL, MariaDB, PostgreSQL, Oracle, and Microsoft SQL Server & Aurora DB engines
    • can be accessed from AWS command-line tools, RDS APIs, or the AWS Management RDS Console.
    • computation and memory capacity of a DB instance is determined by its DB instance class, which can be selected as per the needs
    • supports three storage types: Magnetic, General Purpose (SSD), and Provisioned IOPS (SSD), which differ in performance and price
    • each DB instance has a DB instance identifier, which is a customer-supplied name and must be unique for that customer in an AWS region. It uniquely identifies the DB instance when interacting with the RDS API and AWS CLI commands.
    • each DB instance can host multiple user-created databases or a single Oracle database with multiple schemas.
    • can be hosted in an AWS VPC environment for better control
  • Regions and Availability Zones
    • AWS resources are housed in highly available data center facilities in different areas of the world, these data centers are called regions which further contain multiple distinct locations called Availability Zones
    • Each AZ is engineered to be isolated from failures in other AZs and to provide inexpensive, low-latency network connectivity to other AZs in the same region
    • DB instances can be hosted in different AZs, an option called a Multi-AZ deployment.
      • RDS automatically provisions and maintains a synchronous standby replica of the DB instance in a different AZ.
      • Primary DB instance is synchronously replicated across AZs to the standby replica
      • Provides data redundancy, failover support, eliminates I/O freezes, and minimizes latency spikes during system backups.
  • Security Groups
    • security group controls the access to a DB instance, by allowing access to the specified IP address ranges or EC2 instances
  • DB Parameter Groups
    • A DB parameter group contains engine configuration values that can be applied to one or more DB instances of the same instance type
    • help define configuration values specific to the selected DB Engine for e.g. max_connections, force_ssl , autocommit
    • supports default parameter group, which cannot be edited.
    • supports custom parameter group, to override values
    • supports static and dynamic parameter groups
      • changes to dynamic parameters are applied immediately (irrespective of apply immediately setting)
      • changes to static parameters are NOT applied immediately and require a manual reboot.
  • DB Option Groups
    • Some DB engines offer tools or optional features that simplify managing the databases and making the best use of data.
    • RDS makes such tools available through option groups for e.g. Oracle Application Express (APEX), SQL Server Transparent Data Encryption, and MySQL Memcached support.

RDS Interfaces

  • RDS can be interacted with multiple interfaces
    • AWS RDS Management console
    • Command Line Interface
    • Programmatic Interfaces which include SDKs, libraries in different languages, and RDS API

RDS Multi-AZ & Read Replicas

  • Multi-AZ deployment
    • provides high availability, durability, and automatic failover support
    • helps improve the durability and availability of a critical system, enhancing availability during planned system maintenance, DB instance failure, and Availability Zone disruption.
    • automatically provisions and manages a synchronous standby instance in a different AZ.
    • automatically fails over in case of any issues with the primary instance
    • A Multi-AZ DB instance deployment has one standby DB instance that provides failover support but doesn’t serve read traffic.
    • A Multi-AZ DB cluster deployment has two standby DB instances that provide failover support and can also serve read traffic.
  • Read replicas
    • enable increased scalability and database availability in the case of an AZ failure.
    • allow elastic scaling beyond the capacity constraints of a single DB instance for read-heavy database workloads

RDS Security

  • DB instance can be hosted in a VPC for the greatest possible network access control.
  • IAM policies can be used to assign permissions that determine who is allowed to manage RDS resources.
  • Security groups allow control of what IP addresses or EC2 instances can connect to the databases on a DB instance.
  • RDS supports encryption in transit using SSL connections
  • RDS supports encryption at rest to secure instances and snapshots at rest.
  • Network encryption and transparent data encryption (TDE) with Oracle DB instances
  • Authentication can be implemented using Password, Kerberos, and IAM database authentication.

RDS Backups, Snapshot

  • Automated backups
    • are enabled by default for a new DB instance.
    • enables recovery of the database to any point in time, with database change logs, during the backup retention period, up to the last five minutes of database usage.
  • DB snapshots are manual, user-initiated backups that enable backup of the DB instance to a known state, and restore to that specific state at any time.

RDS Monitoring & Notification

  • RDS integrates with CloudWatch and provides metrics for monitoring
  • CloudWatch alarms can be created over a single metric that sends an SNS message when the alarm changes state
  • RDS also provides SNS notification whenever any RDS event occurs
  • RDS Performance Insights is a database performance tuning and monitoring feature that helps illustrate the database’s performance and help analyze any issues that affect it
  • RDS Recommendations provides automated recommendations for database resources.

RDS Pricing

  • Instance class
    • Pricing is based on the class (e.g., micro) of the DB instance consumed.
  • Running time
    • Usage is billed in one-second increments, with a minimum of 10 mins.
  • Storage
    • Storage capacity provisioned for the DB instance is billed per GB per month
    • If the provisioned storage capacity is scaled within the month, the bill will be pro-rated.
  • I/O requests per month
    • Total number of storage I/O requests made in a billing cycle.
  • Provisioned IOPS (per IOPS per month)
    • Provisioned IOPS rate, regardless of IOPS consumed, for RDS Provisioned IOPS (SSD) storage only.
    • Provisioned storage for EBS volumes is billed in one-second increments, with a minimum of 10 minutes.
  • Backup storage
    • Automated backups & any active database snapshots consume storage
    • Increasing backup retention period or taking additional database snapshots increases the backup storage consumed by the database.
    • RDS provides backup storage up to 100% of the provisioned database storage at no additional charge for e.g., if you have 10 GB-months of provisioned database storage, RDS provides up to 10 GB-months of backup storage at no additional charge.
    • Most databases require less raw storage for a backup than for the primary dataset, so if multiple backups are not maintained, you will never pay for backup storage.
    • Backup storage is free only for active DB instances.
  • Data transfer
    • Internet data transfer out of the DB instance.
  • Reserved Instances
    • In addition to regular RDS pricing, reserved DB instances can be purchased

Further Reading

AWS Certification Exam Practice Questions

  • Questions are collected from Internet and the answers are marked as per my knowledge and understanding (which might differ with yours).
  • AWS services are updated everyday and both the answers and questions might be outdated soon, so research accordingly.
  • AWS exam questions are not updated to keep up the pace with AWS updates, so even if the underlying feature has changed the question might not be updated
  • Open to further feedback, discussion and correction.
  1. What does Amazon RDS stand for?
    1. Regional Data Server.
    2. Relational Database Service
    3. Regional Database Service.
  2. How many relational database engines does RDS currently support?
    1. MySQL, Postgres, MariaDB, Oracle, and Microsoft SQL Server
    2. Just two: MySQL and Oracle.
    3. Five: MySQL, PostgreSQL, MongoDB, Cassandra and SQLite.
    4. Just one: MySQL.
  3. If I modify a DB Instance or the DB parameter group associated with the instance, should I reboot the instance for the changes to take effect?
    1. No
    2. Yes
  4. What is the name of licensing model in which I can use your existing Oracle Database licenses to run Oracle deployments on Amazon RDS?
    1. Bring Your Own License
    2. Role Bases License
    3. Enterprise License
    4. License Included
  5. Will I be charged if the DB instance is idle?
    1. No
    2. Yes
    3. Only is running in GovCloud
    4. Only if running in VPC
  6. What is the minimum charge for the data transferred between Amazon RDS and Amazon EC2 Instances in the same Availability Zone?
    1. USD 0.10 per GB
    2. No charge. It is free.
    3. USD 0.02 per GB
    4. USD 0.01 per GB
  7. Does Amazon RDS allow direct host access via Telnet, Secure Shell (SSH), or Windows Remote Desktop Connection?
    1. Yes
    2. No
    3. Depends on if it is in VPC or not
  8. What are the two types of licensing options available for using Amazon RDS for Oracle?
    1. BYOL and Enterprise License
    2. BYOL and License Included
    3. Enterprise License and License Included
    4. Role based License and License Included
  9. A user plans to use RDS as a managed DB platform. Which of the below mentioned features is not supported by RDS?
    1. Automated backup
    2. Automated scaling to manage a higher load
    3. Automated failure detection and recovery
    4. Automated software patching
  10. A user is launching an AWS RDS with MySQL. Which of the below mentioned options allows the user to configure the InnoDB engine parameters?
    1. Options group
    2. Engine parameters
    3. Parameter groups
    4. DB parameters
  11. A user is planning to use the AWS RDS with MySQL. Which of the below mentioned services the user is not going to pay?
    1. Data transfer
    2. RDS CloudWatch metrics
    3. Data storage
    4. I/O requests per month



13 thoughts on “AWS Relational Database Service – RDS

    1. A standby is in the same region in a different AZ. For MySQL and other databases you can always have a Read Replica in other region and if required promote it in case of DR.

  1. A company wants to implement their website in a virtual private cloud (VPC). The web tier will use an Auto

    Scaling group across multiple Availability Zones (AZs). The database will use Multi-AZ RDS MySQL and should

    not be publicly accessible. What is the minimum number of subnets that need to be configured in the VPC?









    Im guessing option 2

    When you create an RDS instance it is available to all subnets in your VPC via DNS endpoints – you don’t actually specify which subnet it should sit in during creation. RDS is a service, not an EC2 instance. Therefore, number of subnets needed by RDS = 0.

    When you create an RDS instance, select Publicly Accessible – No (another requirement fulfilled).

    As for the web tier – yes, they need a subnet in each AZ.Minimum Number of subnets for Multi Az is 2

    Please suggest

    1. For RDS even though it is a managed service, it required 2 Subnets in different AZ in a multi-az deployment to maintain high availability.
      One subnet hosts the Primary DB instance, while the standby is hosted in the other subnet.
      Only the DNS record is switched during failover.
      You can check the RDS DB Subnet Groups

  2. Under RDS features & Benefits section point seven says IAM users help to control access to RDS databases, it is RDS database or RDS service. I am bit confused.

    1. Its little confusing. The RDS running is called the RDS Instance. I will update it to be RDS Database Service just to avoid any confusion.

    1. You can’t ssh into the server hosting the RDS instance. telnet can only help to make sure the service is up and running on the DB port and not on 22.

  3. Hi,

    I had a question in exam.
    When application server is trying to connect to RDS MySQL instance, its not connecting. Where can we troubleshoot this issue?
    VPC Flow Logs
    RDS MySQL error logs

    I remember these 2 options.

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