# Databases

## Amazon Aurora

* Aurora is a **MySQL and PostgreSQL compatible relational database engine** that **combines the speed and availability of high-end commercial databases**.<br>
* Aurora is **up to five times faster than standard MySQL databases** and **three times faster than standard PostgreSQL databases**.<br>
* It provides the security, availability, and reliability of commercial databases **at 1/10th the cost**.<br>
* Aurora is **fully managed by Relational Database Service (RDS)**.<br>
* Aurora **features a distributed, fault-tolerant, self-healing storage system** that **auto-scales up to 64TB per database instance**.<br>
* It **delivers high performance and availability** with up to **15 low-latency read replicas**, **point-in-time recovery**, **continuous backup to S3**, and **replication across three Availability Zones (AZs)**.

## Amazon Relational Database Service

* RDS makes it easy to set up, operate, and scale a **relational database in the cloud**.<br>
* It provides cost-efficient and resizable capacity while **automating time-consuming administration tasks** such as hardware provisioning, database setup, patching and backups.<br>
* RDS is **available on several database instance types** - optimized for memory, performance or I/O - and provides you with six familiar database engines to choose from, including **Aurora, PostgreSQL, MySQL, MariaDB, Oracle Database, and SQL Server**.<br>
* You can **use the Database Migration Service to easily migrate or replicate your existing databases to RDS**.

## Amazon DynamoDB

* DynamoDB is a **key-value and document database** that delivers **single-digit millisecond performance at any scale**.<br>
* It's a **fully managed, multiregional, multi-master database** with **built-in security, backup and restore, and in-memory caching for internet-scale applications**.<br>
* DynamoDB **can handle more than 10 trillion requests per day** and **support peaks of more than 20 million requests per second**.

## Amazon ElastiCache

* ElastiCache is a web service that makes it easy to deploy, operate, and scale an **in-memory cache in the cloud**.<br>
* The service improves the performance of web applications by allowing you to retrieve information from **fast, managed, in-memory caches**, instead of relying entirely on slower disk-based databases.<br>
* ElastiCache **supports two open-source in-memory caching engines:**
  * **Redis:**
    * A **fast, open source, in-memory data store and cache**.
    * It has many features like **backups and restores**.
    * It has **Multi-AZ and read replicas**.
    * **Has data persistence**.<br>
  * **Memcached:**
    * A **widely adopted memory object caching system**.
    * It is **just a pure cache**.
    * It has **no backups and restores**.
    * **No data persistence**.

## Amazon Neptune

* Neptune is a **fast, reliable, fully-managed graph database service** that makes it easy to build and run applications that work with **highly connected datasets**.<br>
* The core of Neptune is a **purpose-built, high-performance graph database engine optimized for storing billions of relationships** and **querying the graph with milliseconds latency**.

## Amazon DocumentDB (with MongoDB compatibility)

* DocumentDB is a **fast, scalable, highly available, and fully managed document database** service that **supports MongoDB workloads**.

## Amazon S3

* S3 is an **object storage service that offers industry-leading scalability**, data availability, security, and performance.<br>
* Amazon S3 is **designed for 99.999999999% (11 9's) of durability**, and stores data for millions of applications for companies all around the world.


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