# Module 8: Databases

# Section 1: Amazon Realtional Database Service (RDS)
## Unmnagade vs managed services
### Unmanaged
managed by you:
* Scaling
* Fault tolerance
* Availability

More fine-tune control

### Managed
built in the service:
* Scaling
* Fault tolerance
* Availability

Requires less configuration

## Challenges of relational databases
* Server maintenance and energy footprint
* Software installation and patches
* Database backups and high availability
* Limits on scalability
* Data security
* OS installation and patches

## Amazon RDS
:::danger
Managed services that sets up and operates a relational database in the cloud
:::

## Managed services responsabilities
You manage
* App opti

AWS manages:
* OS installation and patches
* Databse software installation and patches
* Database backups
* High availability
* Scaling
* Power and racking and stacking servers
* Server maintenance

## Amazon RDS DB instances

## Amazon RDS in a VPC
* Select IP address range
* Subnets
* Configure routing and access control list

## High availability with Multi-AZ deployement
### 1
* Automatically generates a standby copy in another AZ within the same VPC
* Enhanced availability

### 2

:::warning
If the main database instance fails, Amazon RDS automatically brings the standby instance online.
:::

## Amazon RDS read replicas
Features
* Offers asynchronous replication
* Can be promoted to master if needed

Functionality
* Use for read-heavy database workloads
* Offload read queries

## Use cases

## When to Use Amazon RDS
|Use Amazon RDS when your app requires|Do not use Amazon RDS when your app requires|
|-|-|
|Complex transactions or complex queries|Massive read/write rates|
|A medium to high query or write rate (Up to 30,000 IOPS)|Sharding due to high data size or throughput demands|
|No more than a single worker node or shard|Simple GET or PUT requests and queries that a NoSQL database can handle|
|High durability|Relational database managemnet (RDBMS) customization|

## Amazon RDS: Clock-hour billing and db characteristics
Clock-hour billing
* Resources incur charges when running

Databas characteristics
* Physical capacity
* Engine
* Size
* Memory class

## Amazon RDS: DB purchase type and multiple DB instances
DB purcharse type
* On-demand isntances
* Compute capacity by the hour
* Reserved Instance
* Low, one-time, upfront paymenent for db instances that are reserved with a 1-year or 3-year term

Number of DB instances
* Provision multiple DB instance to handle peak loads

## Amazon RDS storage
Provisioned storage
* No charge
* Bakcup storage up to 100% of db storage for an active db
* Charge (*GB/month*)
* Backup storage for terminated DB instances

Additional storage
* Charge (*GB/month*)
* Backup storage in addition to provisioned storage

## Amazon RDS: Deployement type and data transfer
Requests
* The number of input and output requests that are made to the db

Deployement type - storage and I/O vary, depending on whether you deploy to
* Single AZ
* Multiple AZ

Data transfer
* No charge for inbound data transfer
* Tiered charges for outbound data transfer

# Section 2: Amazon DynamoDB
## Realtion vs non-relation DB

## What is Amazon DynamoDB ?
:::info
Fast and flexibe NoSQL db service for any scale
:::
* NoSQL db tables
* Can be scaled
* Create tables and add items
* Global tables
* Automatically replicates choices across AWS regions
* Virtually unlimited storage
* Items can have differing attributes
* Don't have to migrate schema
* Low-latency queries
* Scalable read/write throughput
* Store data accross multiples facilities
* fault-toleratn architecture
* stored in SSDs
* encrypt data at rest
* set time to live
* Automatically partitions data

## Amazon DynamoDB core components
* Tables, itmes and attributes
* DynamoDB supports 2 different kinds of primary keys
* Partition key
* Sort key

## Items in a table must have a key

# Section 3: Amazon Redshift
## Amazon Redshift
:::info
Fast, fully managed data warehouse, simple and cost-effective to analyze data using SQL and business intellignec tools.
:::

## Introduction to Amazon Redshift

* Fast and fully-managed data warehouse
* Pay for what you use
* Complex analytics queries
* Parallel processing
* Only seconds

## Parallel processing architecture

## Automation and scaling
Automate
* manage
* monitor
* scale

:::warning
Security is built-in with encryption of data.
:::

## Compatibility
* Supports standard SQL
* Connect with SQL clients
* Java connectivity
* Open DB connectivity
* Interact direclty with AWS CLI or management console

## Amazon Redshift use cases
* Enterprise data warehouse (EDW)
* Migrate at a pace that customers are comfortable with
* Experiment without large upfront cost or commitment
* Respond faster to business needs
* Big data
* Low price point for small customers
* Managed service for ease of deployment and maintenance
* Focus more on data and less on database management
* SaaS
* Scale the data warehouse capacity as demand grows
* Add analytic functionality to app
* Reduce hardware and software costs

# Section 4: Amazon Aurora
:::info
MySQL and PostreSQL compatible relational db built for the cloud.
:::

* Enterprise-class relational db
* Compatible with MySQL or PostgreSQL
* Automate time-consuming tasks (such as provisioning, patching, backup, recovery, failure detection and repair)
* Can reduce db costs

## Amazon Aurora service benefits
* Fast and available
* Managed service
* Simple
* Pay-as-you-go
* Compatible

## High availability
* Storing multiple copies through different AZ
* Data backed up to Amazon S3
* Use up to 15 read replica

## Resilient design
* Instant crash recovery
* Does not need to replay the redo log
* Do it on every read operation
* Removes the buffer cache from the db process

# Wrap-up
Which of the following is a fully managed NoSQL db service ?
1. Amazon RDS
2. Amazon DynamoDB
3. Amazon Aurora
4. Amazon Redshift

:::spoiler Answer
Keywords:
* NoSQL

Answer: 2.
:::