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AWS > Databases > Flashcards

Databases Flashcards

1
Q

Which databases support Read Replicas?

A

MySQL
MariaDB
PostgreSQL
Aurora

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2
Q

Which external databases are supported with RDS?

A

SQL Server
MySQL
Oracle
PostgreSQL

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3
Q

Can Read Replicas have Multi-AZ enabled?

A

No, but a source database with Multi-AZ enabled can have Read Replicas

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4
Q

If a database is restored from either an automated backup or a snapshot, what happens to its end point?

A

The restored database will be a new RDB instance with a new end point

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5
Q

What makes Redshift’s advanced compression so efficient?

A

Because Redshift data is stored in columns, it can be compressed more than traditional databases

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6
Q

What are database snapshots?

A

User-initiated backupd of a database which are stored in S3 and retained even if the database is deleted

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7
Q

What is DynamoDB Reserved Capacity?

A

Similar to Resered Instances in EC2, it offers discounted throughput capacity for DynamoDB data, when entering into a 1 or 3 year contract.

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8
Q

Explain Redshift Massive Parallel Processing

A

Redshift automatically distributes data and query load across all compute nodes. It is easy to add nodes to the warehouse, maintaining fast query performance

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9
Q

True or false: You can create a Read Replica from another Read Replica

A

True

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10
Q

What is Elasticache?

A

AWS’s in-memory caching service that provides low-latency cahed data for applications that need it, such as recommendation engines, gaming, or social media

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11
Q

If a database is under a lot of load, what database service would be a good choice to relieve this?

A

Elasticache

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12
Q

What is DMS?

A

Database Migration Service allows you to migrate production database to AWS. AWS manages type transformation, compression and parallel transfer

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13
Q

If managment is running a lot of OLAP queries on a database, what service is a good choice?

A

Redshift. Possibly also Read Replicas in RDS

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14
Q

True or False: A Redshift database can span multiple availability zones

A

False. Redshift is intended for back office analytics and high performance, so it is not built to span AZs

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15
Q

True or false: If an RDS is deleted, its database snapshots are retained

A

True

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16
Q

What is RDS?

A

AWS’s Relational Database Service, which allows you to set up, operate and scale relational databases

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17
Q

How is Redshift encrypted?

A

In-transit using SSL

At rest using AES-256

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18
Q

What is Multi-AZ?

A

It allows you to have an exact syncronous replica of a database in another availability zone. AWS automatically fails over to the replica database if needed

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19
Q

What is the data consistency model for DynamoDB?

A

Users can specify whether they want strongly consistent or eventually consistent.

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20
Q

What is Aurora?

A

A MySQL-compatible relational database engine, much faster than regular MySQL, much chepaer than commercial databases

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21
Q

Can existing unencrypted RDS databases become encrypted?

A

Not directly. To encrypt an existing RDS database, first create a snapshot, copy the snapshot and enable enxryption, then restore the encrypted database

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22
Q

True or false: Automated backup must be enabled on a database before Read Replcias can be created

A

True

23
Q

True or false: Multi-AZ is useful to improve performance of a database

A

False. Multi-AZ is for disaster recovery only, and does not improve performance

24
Q

True or false: If an RDS instance is deleted, the automated backups are retained

A

False

25
Q

Explain the difference between use of Redshift vs EMR?

A

Redshift is intended primarily for business intelligence, while EMR is for Big Data processing.

26
Q

Why would you want to configure DynamoDB with eventual consistency?

A

Eventual consistency maximized read throughput

27
Q

How does Aurora achieve fault tolerance?

A

Automatic replication across three availability zones and automatic failover

28
Q

what are the relative costs of reads and writes with DynamoDB?

A

Writes are much more expensive than reads in DynamoDB, which is why it is best used for read-heavy databases

29
Q

What is the difference between DynamoDB and RDS in terms of scaling?

A

DynamoDB offers automatic scaling with no down time, while RDS requires use of Read Replicas or manual changes in instance size

30
Q

What is EMR?

A

Elastic Map Reduce - It is a service for Big Data processing

31
Q

True or false: Database snapshots are performed automatically

A

False. They are user initiated

32
Q

What is a Read Replica?

A

An asyncronous, read-only copy of a database

33
Q

What in-memory caching engines are supported by Elisticache?

A

Memcached

Redis

34
Q

Explain the multi-node architecture in Redshift

A

There is a Leader Node, which manages client connections, received queries, and distributes them to Compute Nodes. Compute Nodes store data and perform queries and computations. This collection of nodes is often called a cluster

35
Q

How many Read Replicas can you have for a single database?

A

5

36
Q

Describe DynamoDB

A

A fast and flexible NoSQL database service for applications that need low latency at any scale.

37
Q

What might be a cause why you are unable to connect to your RDS instance?

A

You must ensure that the security group allows traffic on port 3306. This can be from an IP, anywhere, or even from another security group

38
Q

Aurora is compatible with what popular database type?

A

MySQL

39
Q

How many Compute Nodes can a Redshift resource have?

A

128

40
Q

What are the use cases for Elasticache?

A

It is intended for read-heavy workloads such as gaming, social media, or compute-heavy workloads such as recommendation engines

41
Q

What are Automated Backups?

A

they allow you to recover your database to any point in time within the “retention period”

42
Q

What is Redshift?

A

Redshift is a petabyte-scale data warehousing service in the cloud, centered around business intelligence

43
Q

What is the default retention period for automated backups?

A

7 days

44
Q

Can a Read Replica be promoted to be its own source database?

A

Yes. The replication with the original source will then be broken, however.

45
Q

What is columnar data storage?

A

Data is stored sequentially in columns rather than as a series of rows. This greatly reduces amount of I/O for analytical processing. This is also referred to as Dense Storage

46
Q

How does DynanoDB ensure high availability and durability?

A

DynamoDB stores three geographically distinct replicas of each table

47
Q

What are Read Replicas primarily used for?

A

They can be used to distribute read performance for read-heavy databases

48
Q

What is an Eventually Consistent Read as applied to DynamoDB?

A

All copies of data are usually consistent within one second

49
Q

What are the two different types of database backups in AWS?

A

Automated backups

Database snapshots

50
Q

What block size does Redshift use for its columnar storage?

A

1024Kb - 1Mb

51
Q

What are the two node types in Redshift?

A

Dense Storage - uses std HDDs at lower cost

Dense Computer - Uses SSDs for fast processing

52
Q

What are minimum and maximum storage limits for Aurora?

A

10Gb minimum, 64Tb maximum, scaled automatically in increments of 10Gb.

53
Q

How many Read Replicas can Aurora support?

A

Up to 15

54
Q

Can you change the RDS DB Instance class after it is created?

A

Yes

AWS (8 decks)

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