RDS & Using Read Replicas

Question 1

What are read replicas?

Answer 1

Read-only copies of your DB that allow you to scale out for performance.

Question 2

How can a read replica be created?

Answer 2

1. Management console

2. CreateDBInstanceReadReplica API

Question 3

Can you have a read replica of a read replica?

Answer 3

Yes, but there may be latency.

Question 4

Would you use a read replica to scale beyond your primary DB’s capacity?

Answer 4

Yes

Question 5

Would you use a read replica to serve traffic while the primary DB is unavailable?

Answer 5

Yes

Question 6

True or False: When running business reports, and performing data warehousing operations, it is best practice to use your primary DB instance?

Answer 6

False. Utilize read replicas for data-intensive workloads so the application is not affected.

Question 7

True or false: You could also import your data into RedShift for data warehousing operations to prevent load on the application DB?

Answer 7

True.

Question 8

Read replicas are supported on which non-Aurora databases?

Answer 8

MySQL
PostgreSQL
MariaDB

Question 9

True or False: Amazon uses a proprietary replication engine for read-replicas?

Answer 9

False. Amazon uses the native replication engines built into their supported DBs for read-replicas.

Question 10

True or False: Aurora uses SSD-Backed virtualized storage layer built for database workloads?

Answer 10

True

Question 11

What does AWS do when a read replica is created?

Answer 11

Takes a snapshot of your DB

Question 12

When creating a read replica, if multi-AZ is not enabled, what will the snapshot be of?

Answer 12

The primary DB.

Question 13

True or False: When a snapshot is made of the primary DB, there is a suspension of I/O for 1 minute?

Answer 13

True

Question 14

When creating a read replica, if multi-AZ is enabled, what will the snapshot be of?

Answer 14

Of the secondary database

Question 15

True or False: When a snapshot is made of the secondary DB, there is a suspension of I/O for 30 seconds?

Answer 15

False. Since the snapshot is not being made of the primary (production) DB, there is no I/O suspension

Question 16

True or False: Read replicas are accessed from the DNS of the primary DB?

Answer 16

False. You are given a new end point.

Question 17

True or false: Read replicas are a new end point, different from the primary and secondary DB (If multi-AZ is enabled)

Answer 17

True.

Question 18

Can you promote a read replica to be its own standalone DB?

Answer 18

Yes

Question 19

What will happen to the primary and secondary DB if a read replica is promoted?

Answer 19

replication will break.

Question 20

Up to how many read replicas per DB are supported?

Answer 20

5

Question 21

True or False: You can have read replicas in different regions?

Answer 21

True

Question 22

Read replica replications are synchronous, or asynchronus?

Answer 22

asynchronous.

Question 23

Multi-AZ DB replications are synchronous, or asynchronus?

Answer 23

synchronous

Question 24

Can read replicas be built off Multi-AZ DB?

Answer 24

Yes, this saves on performance impact.

Question 25

Can read replicas be multi-AZ?

Answer 25

Yes. This is a new service.

Question 26

Can DB snapshots be taken of read replicas?

Answer 26

No. Must use Mult-AZ to offload snapshot I/O performance hit

Question 27

Can automated backups be taken of read replicas?

Answer 27

No. Must use Mult-AZ to offload I/O performance hit

Question 28

Key metric to look for in read replicas?

Answer 28

REPLICA LAG

Question 29

What is replica lag?

Answer 29

The replication latency. The amount of time it takes for a write to the primary DB to replicate to the read replica DB.

Question 30

What is the difference between read replica and Multi-AZ?

Answer 30

1. Read replica is a read only copy of your primary DB and is used for performance and scalability. 2. Multi-AZ is for fail over only, and does not provide performance increases.

Question 31

Can you create a read replica if DB backups are disabled?

Answer 31

No. Backups must be enabled to use read replicas.

Question 32

When applying a modification to a DB, what two options are available for when the changes should be made?

Answer 32

1. During the maintenance window. | 2. Apply Immediately.

Question 33

True or False: When immediately applying a modification, any modifications that are scheduled within the normal maintenance window will also be executed?

Answer 33

True. Be careful when applying changes immediately. If you're making a modification that you don't expect will cause downtime, you may have a scheduled task that does cause downtime, which may lead to unscheduled outages.

Question 34

True or false: A read replica instance type can be different from the primary DB

Answer 34

True.

Question 35

True or false. If the primary DB is gp1, the read replica must also be gp1?

Answer 35

False. You have the option of selecting gp1, io1, or magnetic.