Databases

Question 1

Which RDS databases can be configured as multi-AZ or single-AZ?

Answer 1

• SQLServer
• Oracle
• MySQL
• PostgreSQL
• MariaBD

Question 2

Which RDS database is always multi-AZ?

Answer 2

Amazon Aurora

Question 3

Advantages of RDS?

Answer 3

• up and running in minutes (not days)
• multi-AZ
• failover capability
• automated backups

Question 4

When do we use RDS?

Answer 4

• for online transaction processing (OTP)*
• for customer orders
• for completing large numbers of small transactions in real time

Question 5

When don’t we want to use RDS?

Answer 5

• OLAP (Online Analytical Processing)
• complex queries
• large amounts of data
• data analysis

Instead, use a data warehouse like Redshift, which is optimized for Online Analytics Processing

Question 6

How does Multi-AZ RDS work?

Answer 6

• creates an exact copy of your production database in another AZ
• AWS handles the replication for you

Question 7

What happens in RDS with an Unplanned Failure or maintenance?

Answer 7

• If AWS notices that you lose your primary DB, there is an automatic failover by updating the DNS to point to the secondary DB

Question 8

What is Multi-AZ for?**

Answer 8

• disaster recovery

- NOT improving performance

Question 9

What are Read Replicas for?

Answer 9

• for improving performance
• a read-only copy of your database
• for querying and read-heavy workloads
• NOT for DR

Question 10

Can Read Replicas be Multi-AZ?

Answer 10

Yes,

- can be in different regions

Question 11

How many read replicas can you have per DB?

Answer 11

5

Question 12

Read Replica basics

Answer 12

• a read-only copy of your primary DB in the same AZ, cross-AZ, or cross-region
• used to increase or scale read performance
• great for read-heavy workloads
• takes the load off your primary DB

Question 13

What is Amazon Aurora?

Answer 13

• Amazon’s proprietary DB
• MySQL & PostgreSQL
• combines speed & availability at a low price point

Question 14

How much faster is Aurora than mySQL or PostgreSQL?

Answer 14

• 5x faster than mySQL

- 3x faster than PostgreSQL

Question 15

Aurora Basics

Answer 15

• Storage Auto Scaling - starts with 10 GB. Scales in 10 GB increments up to 128 TB.
• Compute can scale up to 96 vCPUs and 768 GB of memory.

Question 16

How redundant is Aurora?*

Answer 16

2 copies of your data are stored in each AZ, with a minimum of 3 AZs
- it’s really redundant

Question 17

Scaling Aurora

Answer 17

it’s designed to transparently handle the loss of 2 copies of data w/o affecting database write availability and 3 copies of data w/o affecting read availability

Question 18

How is Aurora self-healing?*

Answer 18

• Aurora data blocks and disks are continuously scanned for errors and repaired automatically

Question 19

Aurora Replica limits by type*

Answer 19

Aurora Replicas - up to 15 Aurora replicas

• MYSQL Replicas - up to 5 read replicas
• PostGres Replicas - up to 5 read replicas

Question 20

Aurora Backups*

Answer 20

• automated backups always enabled
• backups do not impact database performance
• can take snapshots (does not impact performance)
• can share snapshots with other AWS accounts

Question 21

Aurora Serverless *

Answer 21

• on demand
• auto-scaling
• for the MySQL and PostGres editions of Aurora
• automatically starts up, shuts down, scales capacity up and down

Question 22

What is Aurora Serverless for?

Answer 22

• infrequent, intermittent, unpredictable workloads

- for questions on exam where you need the performance of Aurora but have spiky workloads

Question 23

Dynamo DB

Answer 23

• Fully managed
• A fast & flexible noSQL database for all applications that need consistent, single-digit-millisecond latency at any scale
• Supports document and key-value data models

Question 24

Dynamo DB use cases

Answer 24

• mobile
• web
• gaming
• ad-tech
• IoT, etc.

Question 25

Dynamo Facts

Answer 25

1. stored on SSD storage 2. spread across 3 geographically distinct data centers 3. eventually consistent reads (by default) 4. strongly consistent reads (as an option)

Question 26

Eventually Consistent Reads *

Answer 26

consistency between all copies of the database is achieved within 1 second

Question 27

Strongly Consistent Reads *

Answer 27

returns a result that reflects all writes that received a successful response prior to the read.

Question 28

Dynamo DB Accelerator (DAX)

Answer 28

- fully managed, highly available, in-memory cache - 10x performance improvement - reduces request time from milliseconds to microseconds, even under load - no need for developers to manage caching logic - compatible with Dynamo Db API calls

Question 29

Dynamo DB On-Demand Capacity

Answer 29

- pay-per-request pricing - balances cost & performance - pay more per request than with provisioned capacity - use for new product launches

Question 30

Dynamo Security

Answer 30

- encryption at rest with KMS - site-to-site VPN - DirectConnect (DX) - IAM policies and roles - fine-grained access - Cloud Watch & Cloud Trail - VPC endpoints

Question 31

Dynamo DB Transactions *

Answer 31

ACID: - Atomic - all changes to the DB must be performed successfully, or not at all - Consistent - data must be in a consistent state before and after the transaction - Isolated - No other processes can change the data while the transaction is running - Durable - the changes made by a transaction must persist.

Question 32

How do you use ACID w/ Dynamo DB?

Answer 32

- by using transactions - transactions provide atomicity, consistency, isolation and durability across 1 or more tables within a single AWS account or region

Question 33

Use Cases for Transactions in DynamoDB*

Answer 33

- apps that need coordinated inserts, deletes or updates to multiple items as part of a single logical business operation - financial transactions, managing orders - building multi-player game engines - coordinating actions across distributed services - up to 25 items or 4 MB of data per transaction

Question 34

What does ACID boil down to?*

Answer 34

All or nothing. No partially successful updates.

Question 35

3 options for reads

Answer 35

- eventual consistency - strong consistency - transactional

Question 36

2 options for writes:

Answer 36

- standard | - transactional

Question 37

Dynamo On-Demand Backup & Restore

Answer 37

- full backups at any time - zero impact on table performance or availability - consistent w/i seconds & retained until deleted - operates in the same region as the source table

Question 38

Dynamo Point in Time Recovery (PITR)

Answer 38

- restore to any point in the last 35 days - incremental backups - not turned on by default - latest restorable point - 5 minutes in the past

Question 39

Dynamo DB Streams

Answer 39

- time-ordered sequence of item-level changes in a table - FIFO - every time your data changes it comes w/ a sequence number - for inserts, updates and deletes - stored for 24 hours - broken into shards - can combine Lambda functions for functionality like stored procedures

Question 40

Shards

Answer 40

collections of stream records with sequential numbers

Question 41

Dynamo Global Tables

Answer 41

a way of replicating your Dynamo DB tables from one region to another - managed multi-master, multi-region replication - great for globally distributed applications* - based on Dynamo DB streams (must be enabled to use Global tables) - multi-region redundancy for recovery or high availability* - no need to re-write your app, just go into the console and turn it on* - replication latency under 1 second