Databases 101

Question 1

What is a relational database analagous to?

Answer 1

A traditional spreadsheet

Question 2

What does RDS stand for?

Answer 2

Relational Database Servers

Question 3

What are the 6 flavors of relational databases engines that are compatible with Amazon?

Answer 3

• SQLServer
• MySQLServer
• Aurora
• Oracle
• PostgreSQL
• MariaDB

Question 4

What are the 2 key features of RDS? What are they primarily for?

Answer 4

• Multi-AZ (for distaster recovery)
• Read Replicas (for performance)

Question 5

Does RDS Multi-AZ require changing the connection string?

Answer 5

If you lose access to your primary database, AWS can automatically point incoming requests to your secondary database without changing the connection string

Question 6

How do Read Replicas work in RDS?

Answer 6

• There is no automatic failover. If your primary instance goes down, you’ll need to create a new URL to connect to the secondary instance
• All writes to the primary instance are copied over to the read replica(s)

Question 7

Suppose you want to be able to handle a surge of incoming traffic to your RDS instance and scale out your application. What key feature of RDS would you use to do this?

Answer 7

Read Replicas

Question 8

What is the maximum number of read replicas that can be made from a single primary RDS instance?

Answer 8

up to 5 copies

Question 9

What is a non-relational database best analagous to?

Answer 9

A JSON Object

Question 10

What does OLTP stand for?

Answer 10

Online Transaction Processing

Question 11

What does OLAP stand for?

Answer 11

Online Analytics Processing

Question 12

What is the difference between OLTP and OLAP?

Answer 12

• Big difference is in the types of queries you will run
• OLTP is for a specific transaction
• OLAP will pull in a lot of data

Question 13

What is Amazon’s data warehousing solution?

Answer 13

Redshift

Question 14

What is Elasticache?

Answer 14

Elasticache is a web service that makes it easy to deploy, operate, and scale an in-memory cache in the cloud.

Question 15

What is the benefit of using Elasticache?

Answer 15

• Elasticached is used to speed up performance of existing databases
• frequent identical queries
• Elasticache improves the performance of web applications by allowing you to retrieve information from fast, managed in-memory caches, instead of relying entirely on slower, disk-based databases.

Question 16

What are the two types of open-source in-memory caching engines that Elasticache supports?

Answer 16

• Memcached
• Redis

Question 17

Does RDS run on virtual machines?

Answer 17

Yes

Question 18

How can you log in to the OS of an RDS instance?

Answer 18

You can’t

Question 19

How can you patch the OS or database of an RDS instance?

Answer 19

This is Amazon’s responsibility (you can’t)

Question 20

Is RDS Serverless?

Answer 20

No, (except for Aurora)

RDS runs on virtual machines

Question 21

What is the use case for Elasticache?

Answer 21

Use Elasticache to increase DB and web application performance

Question 22

Does memcached support Multi-AZ?

Answer 22

No

Question 23

Does memcached support Backup and Restore?

Answer 23

No

Question 24

Does memcached support multi-threaded performance?

Answer 24

Yes

Question 25

Does redis support multi-threaded performance?

Answer 25

**No**

Question 26

Does redis support Multi-AZ?

Answer 26

**Yes**

Question 27

Does Redis support Backup and Restore?

Answer 27

**Yes**

Question 28

What is **AWS DMS** used for?

Answer 28

DMS allows you to **migrate services from one source to AWS**

Question 29

What is the difference between a **homogenous migration** and a **heterogeneous migration**?

Answer 29

* Homogenous migrations go between the same database engines * Heterogenous migrations go between two different database engines

Question 30

What types of infrastructures can be used as a DMS Source?

Answer 30

The source can be: * On-premises * inside AWS itself * another cloud storage provider (like Azure)

Question 31

What does **SCT** stand for?

Answer 31

**S**chema **C**onversion **T**ool

Question 32

Do you need AWS SCT for a homogenous migration?

Answer 32

**No**

Question 33

Do you need AWS SCT for a heterogenous migration?

Answer 33

**Yes**

Question 34

What concerns need to be balanced when cacheing on AWS?

Answer 34

Cacheing is a balancing act between **up-to-date information** and **latency**

Question 35

What are the services on AWS that use cacheing?

Answer 35

* CloudFront * API Gateway * Elasticache (memchached and redis) * DynamoDB Accelerator (DAX)

Question 36

What does **EMR** stand for?

Answer 36

**E**lastic **M**ap-**R**educe

Question 37

What is AWS EMR?

Answer 37

EMR is the industry-leading cloud _big data platform_ for processing vast amounts of data using open-source tools like Apache Splunk, Apache hive, Apache HBase, Apache Flink, Apache Hudi, and Presto

Question 38

At what scale can AWS EMR run analysis?

Answer 38

EMR can run **petabyte-scale** analysis

Question 39

What is the cost-saving estimate for EMR over traditional on-premises solutions?

Answer 39

EMR offers analysis at **less than half the cost** of traditional on-premises solutions

Question 40

What is the estimated speed increase of EMR over Apache Spark?

Answer 40

**3x** faster

Question 41

What is a **cluster** in AWS EMR?

Answer 41

A **collection of EC2 instances**, each of which is called a **node**

Question 42

What are the three node types in EMR?

Answer 42

* Master Node * Core Node * Task Node

Question 43

What is the purpose of a master node in EMR?

Answer 43

The master node manages the cluster and tracks the status of tasks. ## Footnote **Every cluster has a master node**

Question 44

What is the purpose of a core node in EMR?

Answer 44

A core node **runs tasks and stores data in HDFS**. Multi-node clusters have at least one core node

Question 45

What does **HDFS** stand for?

Answer 45

**H**adoop **D**istributed **F**ile **S**ystem

Question 46

What is the purpose of a task node in AWS EMR?

Answer 46

A task node runs tasks, but does NOT store data in HDFS they are optional for your cluster.

Question 47

Suppose your EMR cluster wants to be able view log files even after the master node terminates. Is this possible?

Answer 47

**Yes**, **you can configure a cluster to periodically archive the log files stored on the master node to S3**. This ensures log files are available after the cluster terminates, whether through a normal shutdown or due to an error. Note that **this is only possible when you are creating the cluster for the first time**

Question 48

How often does EMR archive log files to S3?

Answer 48

**5-minute intervals**

Question 49

By default, how is log data stored in EMR?

Answer 49

By default, log data is stored **on the master node**

Question 50

Can Elasticache be used for Pub/Sub type systems?

Answer 50

**Yes**

Question 51

Can you encrypt an unencrypted database snapshot?

Answer 51

**No**