Databases

Question 1

Does Multi-AZ RDS allow to create instances in different regions?

Answer 1

No, only in different AZs of the same region

Question 2

How would you store session data?

Answer 2

With ElastiCache
In alternative, it can be done by activating sticky session in ELB, but this might cause unbalanced traffic across instances

Question 3

Can you combine Read Replicas and Multi-AZ in a RDS instance?

Answer 3

Yes

Question 4

In a Multi-AZ RDS, what happens if the primary instance fails?

Answer 4

A secondary replica instance is elected as a primary source of replication

Question 5

Can you use RDS Cross Region for write failover?

Answer 5

No, Cross Region is used to create Read Replicas across multiple regions. Use Multi-AZ instead

Question 6

What does RDS use for database and log storage?

Answer 6

EBS Volume

Question 7

You try to connect to your RDS instance and you receive an “Error setting/closing connection: Connection refused”. What is most likely the cause of the connection failure?

Answer 7

Incorrect DNS name or endpoint was used to connect to the RDS instance

Question 8

You have a RDS instance. Which services are you going to pay for it between:
- Data transfer
- RDS CloudWatch metrics
- Data storage
- I/O requests per month

Answer 8

Everything excepts CloudWatch metrics

Question 9

How many types of secondary indexes does DynamoDB support?

Answer 9

2, Local secondary index and Global secondary index

Question 10

Does Aurora support schema changes?

Answer 10

Yes

Question 11

What type of replication is supported by Multi-AZ RDS instances?

Answer 11

Synchronous replication

Question 12

Does Aurora support cross-region replication?

Answer 12

Only for MySQL, not for PostgreSQL

Question 13

What is the difference in Aurora between cross-region logical replication and cross-region physical replication?

Answer 13

Physical replication can only replicate to one secondary region, logical replication can replicate to multiple regions

Question 14

Can you assign network capacity to RDS instances?

Answer 14

Yes

Question 15

What type of replication are RDS Multi-AZ and Read Replicas?

Answer 15

Multi-AZ is syncronous
Read Replicas is asynchronouse and can be within AZ, Cross-AZ, Cross-Region

Question 16

Can you enable storage auto scaling for RDS?

Answer 16

Yes, if you enable it these factors apply:

Free available space is less than 10 percent of the allocated storage.
The low-storage condition lasts at least five minutes.
At least six hours have passed since the last storage modification.
The maximum storage threshold is the limit that you set for autoscaling the DB instance.

Question 17

Can you set standby instances for Aurora Multi-AZ?

Answer 17

No, only for RDS Multi-AZ

Question 18

What traffic charges involve data replication with RDS?

Answer 18

There are changes only between replication through different regions. No traffic charges for replication across AZs of the same region

Question 19

What’s the difference between a RDS with Multi-AZ or RDS with standby read replicas?

Answer 19

Read replicas do not support automatic failover, promotion to primary instance is manual.
Multi-AZ failover is automatic

Question 20

What’s the difference between RDS Multi-AZ and Aurora Multi-AZ?

Answer 20

RDS: failover is done with standby instance
Aurora: failover is done with read replica (no standby instances)
https://aws.amazon.com/rds/features/read-replicas/

Question 21

What’s the maximum retention period for automated backups in RDS?

Answer 21

35 days. To increase the retention, you need to create a backup plan with AWS Backup

Question 22

How can you change the instance class of a running Aurora db to serverless?

Answer 22

The only way to do that without down time is to use AWS Database Migration Service with ongoing replication

Other methods (with downtime) are:
Take a snapshot and use that to create a new Aurora instance
Add an Aurora replica to the cluster with serverless type. Failover to the read replica and promote it to primary

Question 22

What happens if you have a serverless Aurora DB and it fails?

Answer 22

Aurora tries to create a new database instance in a new AZ

Question 22

What happens if you have a single instance Aurora DB (not serverless) and it fails?

Answer 22

Aurora tries to create a new database instance in the same AZ

Question 23

Are there data transfer charges for replicating RDS across read replicas in the same region?

Answer 23

No, charges apply only for replicating to a different region