databases.txt

AWS Database Types
Maximun size: 16 TB. If larger, consider Redshift

RDS - OTLP (Online Transaction Processing)
  - SQL Server
  - Oracle
  - MySQL
  - PostgreSQL
  - Amazon Aurora
  - MariaDB
- DynamoDB
- RedShift OLAP (Online Analytics Processing, Datawarehousing)
- Elasticache

 Non-Relational Database Structure
 - Database
   - Collection (table)
     - Document (row)
       - Key/Value Pairs (fields)

Data Warehousing
- Used for Business Intelligence (Cognos, Jaspersoft, etc.)
- OLTP Vs. OLAP
--- OLTP (Online Transaction Processing)
--- --- Order number 2120121
--- --- Pulls up a row of data (name, date, address, status)
--- OLAP (Online Analytics Processing, used for Datawarehousing)
--- --- Pull in large number of records
--- --- Uses different type of architecture for database and infrastructure

Elasticache
- Web service that makes it easy to deploy, operate, and scale in-memory cache in the cloud
- Types
  - Memcached
  - Redis



Summary
Database Types
  - RDS (OLTP)
    - SQL
    - MySQL
    - PostgreSQL
    - Oracle
    - Aurora
    - MariaDB
  - DynamoDB (NoSQL)
  - RedShift (OLAP)
  - Elasticache (in-memory)
    - Memcached
    - Redis

Multi-AZ
- Used for DR
- Not used for performance gains

Read Replicas
- Used for scaling, performance gains
- You can have up to 5 Read Replicas
- You can have replicas of replicas (higher latency)
- Can be in a different region

Aurora scaling
- 2 copies of data in each AZ, 3 AZ's minimunm (total of 6 copies)
- Designed to handle losses transparently
- Self-healing storage

Aurora Replicas
- Up to 15 Replicas

MySQL Replicas
- Up to 5 Replicas

DynamoDB vs RDS
- DynamoDB offers "push button" scaling
- RDS requires bigger instance size or to add Read Replica

DynamoDB
- stored on SSD storage
- spread across 3 geographically distinc data centers
- Types
  - eventually consistent reads (default)
  - strongly consistent reads

Redshift Configuration
- Single Node (160GB)
- Multi-Node
  - Leader Node (manages client connections)
  - Compute Node (stores data, performs queries, up to 128 nodes)

Elasticache
- Memcached
  - Multi-AZ NOT available
- Redis
  - Multi-AZ available
  
Two types of backup:
- Automated -> retention period: between 1 and 35 days
- Database snapshots
	Stored in S3. Not deleted when the RDS instance is deleted

Encryption at rest: KMS. Can't enable encryption on existing DB. Must perform a copy and enable the encryption on the restored copy.