Databases 101

Question 1

What is RDS?

Answer 1

It is Amazon’s Relational Database System.

Question 2

What is RDS Multi AZ?

Answer 2

This is for disaster recovery. If the primary database fails AWS automatically shifts requests over to the secondary database, called FailOver.

Question 3

What is RDS Read Replicas?

Answer 3

This is for performance. It uses one a Primary database that can be used for writes and reads, but a Secondary database also exists for two purposes, redundancy, and to reduce the number read requests on the Primary database which can slow the Primary performance. Read Replicas does not support FailOver.

Question 4

How many Read Replicas are allowed?

Answer 4

Up to 5, and you can have Read Replicas of Read Replicas, but this increase latency. The Read Replicas also can be in different AZs or Regions that the Primary dB.

Question 5

What is OLTP vs OLAP?

Answer 5

Online Transaction Processing is database architecture that specifically for finding information, ex. an order number and related info.

Online Analytics Processing is another architecture for database, but is designed for querying large numbers of records, and running calculations on them.

Separate databases allows each architecture to run as efficiently as it can.

Question 6

What is ElastiCache?

Answer 6

It is a web service that allows for easy deployment of in memory cache in the cloud, like the RAM for a computer. It supports Memcache and Redis.

Question 7

What AWS Services use OLTP?

Answer 7

RDS uses Online Transaction Processing for mysql, oracle, and aurora databases.

Question 8

What AWS Services use OLAP?

Answer 8

RedShift is a data warehouse that uses Online Analytics Processing for querying large record sets.

Question 9

Who is responsible for patches on RDS?

Answer 9

RDS runs on virtual machines, and so it is not possible to log into the OS and patch. AWS is responsible for patching and updates.

Question 10

Is RDS Serverless?

Answer 10

No, RDS is not serverless, with the exception of Aurora dB, which has a serverless option.

Question 11

What are the two types of Backups for RDS?

Answer 11

1. Automated Backups - allows recovery any time up to 35 days. Takes full backups plus transaction logs.
2. Database Snapshots - manual, are stored even after the RDS instance is deleted.

Question 12

What does RDS use for Encryption at Rest?

Answer 12

It uses the AWS Key Management Service, KMS.

Question 13

True or False: Read Replicas require automatic backups to be turned on.

Answer 13

True; they cannot be deployed with automatic backups.

Question 14

Can a Read Replica be promoted to a master dB?

Answer 14

Yes, however it breaks the replication to that dB.

Question 15

True or False: It is possible to force a Multi AZ failover into another AZ?

Answer 15

True; with Multi AZ turned on, you can reboot the RDS instance with failover to force the RDS instance to simulate a disaster scenario.

Question 16

What is Dynamo dB?

Answer 16

A NoSql database stored on SSD storage, spread across 2 geographically distinct data centers. It has Eventual Consistent Reads by default, and supports Strongly Consistent Reads.

Question 17

What is the difference between Eventual Consistency Reads and Strongly Consistent Reads?

Answer 17

Eventual Consistent Reads means consistency across all copies of data occurs within a second.

Strongly Consistent Reads means returns a results for all writes that received a success response prior to the read request. This is designed for applications that need near read after write consistency.

Question 18

What is RedShift?

Answer 18

It is AWS’ data warehouse service. It uses OLAP, and is only available in one AZ. The backup retention period is up to 35 days, and Redshift always attempts to maintain at least 3 copies of the data, and can also replicate snapshots to S3 in another region for disaster recovery.

Question 19

What is Aurora?

Answer 19

Amazon’s relational database.

Starts w/ 10Gb of storage and scales in 10Gb increments up to 64 Tb.

Compute resources can scale up to 32 vCPUs and 244Gb of memory.

Two copies of data are contained in each AZ with a minimum of 3 AZs, so 6 copies of the data.

Aurora Storage is automatically repaired when errors are detected.

Question 20

How many AZs can Aurora lose with no impact to database write and read availability?

Answer 20

Write - 2AZs

Read - 3 AZs

Question 21

How many Read Replicas can Aurora support?

Answer 21

Up to 15, but Cross Region is not supported. There are 3 types of replicas, Aurora, MySQL, and Postgres. Failover is only supported for Aurora replicas.

Question 22

What is Aurora Serverless?

Answer 22

A simple, cost effective option for infrequent, intermittent, unpredictable workloads. You pay only when someone is requesting data, such as via website.

Question 23

What is the use case for ElastiCache?

Answer 23

It is used to increase database and web application performance.

Question 24

What are two options to increase the performance of an overloaded database?

Answer 24

1. Add a Read Replica and point all the reads to the replica.
2. Add ElastiCache

Question 25

True or False: Redis is Multi AZ?

Answer 25

True; it is Multi AZ, and it allows for back ups and restores or Redis.