Databases in AWS

Question 1

What is Amazon RDS?

Answer 1

A managed relational database service that is compatible with many of the most used database engines, such as MySQL, PostgreSQL, Oracle etc.

Question 2

How do manual and automatic backups work with RDS?

Answer 2

Automated backups enable point-in-time-restore capability, but expire after 35 days.
Manual backups are kept for longer than this and thus can be used for longer term recovery.

Question 3

What two engines is Aurora compatible with?

Answer 3

PostgreSQL and MySQL

Question 4

When is the serverless version of Aurora appropriate?

Answer 4

For intermittent or unpredictable workloads

Question 5

What is the strength of Aurora’s storage set up?

Answer 5

Data is stored in 6 replicas across 3 AZs, making it highly available and self-healing

Question 6

What is the fastest way to make a new Aurora cluster from an existing one?

Answer 6

Cloning - faster than restoring a snapshot

Question 7

What is ElastiCache?

Answer 7

A managed Redis/Memcached database service that utilises an in-memory store to deliver queries with sub-ms latency

Question 8

What is one downside/serious consideration associated with using ElastiCache?

Answer 8

It will probably require modifications to your application’s code

Question 9

What is an example of a use case for ElastiCache?

Answer 9

Key/value store, frequent reads (but not often written), cache results for DB queries, store session data for websites

Question 10

What high availability feature does DynamoDB have as default?

Answer 10

Multi-AZ deployment

Question 11

What is DynamoDB?

Answer 11

Proprietary AWS noSQL database that is useful for databases where you need a flexible or evolving schema

Question 12

What are the two DynamoDB backup options?

Answer 12

Automated or manual

Question 13

How is security, authorisation and authentication handled for DynamoDB?

Answer 13

Through IAM

Question 14

What is DocumentDB specialised for? Does it use SQL?

Answer 14

JSON data
No, DocumentDB is a NoSQL database service

Question 15

What is Neptune?

Answer 15

A fully managed, highly available graph database.

Question 16

What is Amazon Keyspaces?

Answer 16

A fully managed Apache Cassandra distributed database.

Question 17

What query language is used to query an Amazon Keyspace database?

Answer 17

Cassandra Query Language

Question 18

What is QLDB? What does this stand for?

Answer 18

A ledger of financial transactions that are immutable and cryptographically verifiable

Question 19

What would a QLDB be used for?

Answer 19

Reviewing the history of all the changes made to application data over time

Question 20

What is the difference between QLDB and Amazon Managed Blockchain?

Answer 20

QLDB has no decentralisation component in accordance with financial regulations

Question 21

What is Amazon Timestream?

Answer 21

A fully managed time series database with built-in analytics functions

Question 22

Are RDS read replicas updated synchronously or asynchronously?

Answer 22

Asynchronously

Question 23

What would be the equivalent AWS service used for a MongoDB database?

Answer 23

A DocumentDB database

Question 24

What is the simplest way to increase the storage of an RDS instance if you need to?

Answer 24

Enable autoscaling on that instance

Question 25

What service would be used for caching popular DynamoDB results?

Answer 25

DynamoDB Accelerator (DAX)

Question 26

How do you encrypt an RDS database?

Answer 26

Create an encrypted snapshot and then restore the database from the encrypted snapshot

Question 27

What is lazy loading?

Answer 27

A caching strategy where data is only updated in the cache if it is forced to do so (i.e. there was a cache miss). There are no forced updates when the backend database is updated

Question 28

What is a downside of lazy loading?

Answer 28

Data can easily become stale as there is no forced updates when data in the actual backend database is changed or updated

Question 29

What is write-through with ElastiCache? What is the benefit of write-through? What is the downside?

Answer 29

A caching strategy where new data is written simultaneously to the cache and the database.
Benefit: Data is always up to date
Downside: Slightly increases latency

Question 30

What is a benefit of lazy loading?

Answer 30

There is minimal data kept in the cache itself, so it can be small in size and there is nothing unnecessary in there