# Overview

* Storing data on disk (EFS, EBS, EC2 Instance Store, S3) can have its limits
* Sometimes, you want to store data in a database...
* You can structure the data
* You build indexes to efficiently query / search through the data
* You define relationships between your datasets
* Databases are optimized for a purpose and come with different

  features, shapes, and constraints

### Relational Databases

• Looks just like Excel spreadsheets, with links between them!

• Can use the SQL language to perform queries/lookups

<figure><img src="/files/FMi4rAB6GCRRTDV3urNW" alt=""><figcaption></figcaption></figure>

### NoSQL Databases

* NoSQL = non-SQL = non relational databases
* NoSQL databases are purpose built for specific data models and have flexible schemas for building modern applications.
* Benefits:
  * Flexibility: easy to evolve data model
  * Scalability: designed to scale-out by using distributed clusters&#x20;
  * High-performance: optimized for a specific data model
  * Highly functional: types optimized for the data model
* Examples: Key-value, document, graph, in-memory, search databases
* JSON = JavaScript Object Notation
* JSON is a common form of data that fits into a NoSQL model
* Data can be nested
* Fields can change over time
* Support for new types: arrays, etc...

<figure><img src="/files/eNMh0JGcAdOwIc8orDsc" alt=""><figcaption></figcaption></figure>

### Databases & Shared Responsibility on AWS

• AWS offers use to manage different databases

• Benefits include:

* Quick Provisioning, High Availability, Vertical and Horizontal Scaling&#x20;
* Automated Backup & Restore, Operations, Upgrades
* Operating System Patching is handled by AWS
* Monitoring, alerting

• Note: many databases technologies could be run on EC2, but you must handle yourself the resiliency, backup, patching, high availability, fault tolerance, scaling...


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