5-Databases

Question 1

What engines does RDS support?

Answer 1

Aurora, MySQL, MariaDB, PostgreSQL, Oracle and MySQL server

Question 2

Are RDS instances public?

Answer 2

They are private by default and never given a public IP address, but they can have a public DNS

Question 3

What is required for EC2 instances to connect to an RDS instance?

Answer 3

Port 3306 must be opened in the security groups

Question 4

How can data be kept safe on RDS?

Answer 4

With backups and snapshots

Question 5

How do RDS backups work?

Answer 5

Automatic backups are enabled by default and allow point-in-time restores within the retention period (up to 35 days)

They take a full daily snapshot and store transaction logs during the day - it can restore down to the second

Data is backed up to S3, a 10 GB instance gets 10 GB of free S3 storage

The backups are automatically deleted if the instance is deleted

Question 6

How do RDS snapshots work?

Answer 6

They can be created on demand.

They are not removed if the instance is deleted

Question 7

What happens if RDS is restored from a backup/snapshot?

Answer 7

A new instance is created i.e. with a new DNS name

Question 8

How can high-availably for RDS be assured?

Answer 8

With multi-AZ deployments in which changes are synchronously copied to another AZ

This is for disaster recovery only - not performance

Question 9

How is data on RDS protected?

Answer 9

Data can be encrypted at rest for all engines using KMS

Existing instances can’t be encrypted - take a snaphot, encrypt it and restore

Question 10

How can RDS performance be improved?

Answer 10

With read replicas, in which any writes are asynchronously replicated

There can be up to 5 read replicas but only for Aurora, MySQL, PostgreSQL and MariaDB

Question 11

Where are read replicas stored?

Answer 11

They can be in the same AZ, multiple AZs or a different region

Question 12

What must be enabled for read replicas to be used?

Answer 12

Automatic backups

Question 13

How are read replicas useful for analytics?

Answer 13

They can be promoted to full instances, which is useful for OLAP

Question 14

How does Redshift work?

Answer 14

Support single or multiple node distributions, but in a single AZ

It uses columnar storage

Question 15

What is Aurora?

Answer 15

A managed database service that automatically scales up to 64 TB.

Question 16

How does Aurora ensure data durability?

Answer 16

Two copies of the data are stored in each of the three AZs.

It maintains write capacity if two disks are lost, and can be read if up to three failed

However, the VM itself is only in one AZ so failover is required if the AZ goes down

Question 17

How is Aurora performance optimised?

Answer 17

There can be up to 15 Aurora read replicas that fail-over automatically to become the master

There can only be 5 MySQL replicas and they can’t automatically failover