AWS Fundamentals: RDS/RDS Custom

Question 1

What is AWS RDS?

Answer 1

AWS RDS (Relational Database Service) is a managed service that allows you to run and manage relational databases in the cloud. It supports several SQL-based database engines and automates tasks such as provisioning, patching, backups, and scaling.

Question 2

What are the database engines supported by AWS RDS?

Answer 2

PostgreSQL
MySQL
MariaDB
Oracle
Microsoft SQL Server
IBM DB2
Amazon Aurora (AWS proprietary database)

Question 3

Why use AWS RDS over deploying a database on EC2?

Answer 3

Automated provisioning and OS patching
Continuous backups with Point in Time Restore
Monitoring dashboards
Read replicas for improved read performance
Multi-AZ deployments for disaster recovery
Scaling capabilities (vertical and horizontal)
EBS-backed storage

Question 4

What is RDS Storage Auto Scaling?

Answer 4

RDS Storage Auto Scaling automatically increases the storage capacity of your database when it is running out of space. This happens without any downtime, and the scaling is done based on pre-defined thresholds.

Question 5

How does RDS Storage Auto Scaling work?

Answer 5

RDS Storage Auto Scaling is triggered when the free storage space falls below 10% of the allocated storage, and this condition persists for more than 5 minutes. It will only trigger if 6 hours have passed since the last storage modification. You can set a maximum storage threshold to prevent unlimited scaling.

Question 6

What are the benefits of RDS Storage Auto Scaling?

Answer 6

Prevents manual intervention: No need to manually increase storage.
Supports unpredictable workloads: Automatically scales when needed.
No downtime: RDS handles storage scaling without requiring database downtime.
Works with all RDS database engines.

Question 7

What is Point in Time Restore in AWS RDS?

Answer 7

Point in Time Restore allows you to restore an RDS database to a specific timestamp. This is useful for recovering from unintended data loss or corruption.

Question 8

What is Multi-AZ in AWS RDS?

Answer 8

Multi-AZ is a deployment option in AWS RDS that automatically replicates your database to a standby instance in a different Availability Zone (AZ) for high availability and failover. This helps improve disaster recovery.

Question 9

What is the maximum storage threshold in RDS?

Answer 9

The maximum storage threshold is the upper limit that you can define for the automatic storage scaling in RDS. It prevents the storage from growing beyond a specified capacity.

Question 10

Can you SSH into RDS instances?

Answer 10

No, you cannot SSH into RDS instances. AWS manages the underlying infrastructure and prevents direct access to the EC2 instances running the RDS databases.

Question 11

What are the scaling capabilities of AWS RDS?

Answer 11

AWS RDS supports both vertical scaling (changing instance size) and horizontal scaling (using read replicas). You can increase the database instance size or add read replicas to improve read performance.

Question 12

Does AWS RDS provide automatic backups?

Answer 12

Yes, AWS RDS automatically creates backups of your database. These backups are stored for a retention period that you can configure, and you can restore the database to any point within this retention period.

Question 13

What are Read Replicas in AWS RDS?

Answer 13

RDS Read Replicas are used to scale reads in applications. They provide additional read capacity by asynchronously replicating data from the primary database instance. They help offload read-heavy workloads without impacting the performance of the primary database.

Question 14

How many Read Replicas can you create in AWS RDS?

Answer 14

You can create up to 15 Read Replicas in AWS RDS.

Question 15

What is the replication method for RDS Read Replicas?

Answer 15

RDS Read Replicas use asynchronous replication, meaning changes made in the primary database are eventually propagated to the replicas. This results in eventual consistency, where there may be a delay in data appearing on the Read Replicas.

Question 16

Can Read Replicas be promoted to independent databases?

Answer 16

Yes, a Read Replica can be promoted to its own independent database instance, allowing it to accept write operations and function as a standalone database.

Question 17

What types of operations can be performed on RDS Read Replicas?

Answer 17

RDS Read Replicas are read-only by design. They can only handle SELECT queries, and not INSERT, UPDATE, or DELETE operations.

Question 18

What are the networking cost implications of using RDS Read Replicas?

Answer 18

Same region, different Availability Zones (AZs): No additional networking cost (managed service).

Cross-region Read Replicas: There is a network cost for replicating data across regions.

Question 19

What is the primary use case for RDS Read Replicas?

Answer 19

RDS Read Replicas are typically used for offloading read-heavy workloads such as reporting or analytics. By using a Read Replica, you can avoid overloading the primary database with read traffic.

Question 20

Can RDS Read Replicas be used for scaling writes?

Answer 20

No, RDS Read Replicas are designed for read scaling only. They cannot handle write operations, which must be directed to the primary database.

Question 21

What is RDS Multi-AZ used for?

Answer 21

RDS Multi-AZ is designed for disaster recovery. It provides a synchronous replication between the primary database instance and a standby instance in a different Availability Zone. This ensures high availability and failover protection.

Question 22

How does RDS Multi-AZ handle failover?

Answer 22

If the primary database instance in RDS Multi-AZ fails (due to an AZ failure or database issues), the standby instance is automatically promoted to become the new primary database. The DNS name of the database remains the same, so applications continue to work with minimal disruption.

Question 23

What is the replication method for RDS Multi-AZ?

Answer 23

RDS Multi-AZ uses synchronous replication, meaning that every write to the primary database is also replicated immediately to the standby instance. Both databases stay in sync.

Question 24

Can you perform read operations on the standby instance in RDS Multi-AZ?

Answer 24

No, it cannot be used for read or write operations unless it is promoted to become the primary instance.

Question 25

What is the difference between RDS Read Replicas and RDS Multi-AZ?

Answer 25

Read Replicas: Used to scale reads by creating multiple copies of the database that handle read traffic. They are asynchronously replicated and can be promoted to independent databases.

Multi-AZ: Used for disaster recovery by providing synchronous replication to a standby instance in another Availability Zone. It offers high availability and automatic failover but does not scale reads.

Question 26

Can RDS Read Replicas be configured as Multi-AZ?

Answer 26

Yes, you can configure RDS Read Replicas as Multi-AZ for disaster recovery, allowing the replica to be a standby database in a different Availability Zone. This setup ensures high availability in case of primary database failure.

Question 27

What happens behind the scenes when you enable Multi-AZ for an RDS database?

Answer 27

When enabling Multi-AZ, AWS will:

Take a snapshot of the primary database.
Restore the snapshot to a new standby instance in another Availability Zone.
Establish synchronous replication between the primary and standby databases.

Question 28

Is RDS Multi-AZ used for scaling?

Answer 28

No, RDS Multi-AZ is not used for scaling read or write traffic. It is designed solely for high availability and disaster recovery. For scaling reads, you would use Read Replicas.

Question 29

Can you change the Multi-AZ setting for an RDS database instance after creation?

Answer 29

Yes, you can modify an existing RDS instance to enable or disable Multi-AZ deployment. This can be done with zero downtime.

Question 30

What is RDS Custom?

Answer 30

RDS Custom is an AWS service that allows full access to the underlying operating system and database for Oracle and Microsoft SQL Server databases. Unlike standard RDS, which abstracts the OS, RDS Custom provides more control and customization.

Question 31

Which database engines are supported by RDS Custom?

Answer 31

RDS Custom supports Oracle and Microsoft SQL Server databases.

Question 32

What additional capabilities does RDS Custom provide compared to standard RDS?

Answer 32

Access the underlying EC2 instance using SSH or SSM Session Manager.

Perform customizations on the operating system and database.

Apply custom patches, configure internal settings, and enable native features.

Question 33

What is the role of SSH or SSM Session Manager in RDS Custom?

Answer 33

SSH or SSM Session Manager allows you to access the underlying EC2 instance behind RDS Custom for database or OS customizations.

Question 34

What should you do before performing customizations in RDS Custom?

Answer 34

Deactivate automation mode to prevent RDS from automatically performing maintenance, scaling, or updates during the customization process.

Take a database snapshot before making changes to ensure you can recover from any mistakes.

Question 35

What is the primary difference between RDS and RDS Custom?

Answer 35

RDS: Fully managed service, with no access to the underlying OS or database, and AWS handles all the database and operating system management.

RDS Custom: Offers access to the underlying EC2 instance and operating system, providing full admin control over the database and OS, limited to Oracle and SQL Server engines.