Amazon Relational Database Service
Amazon Relational Database Service or Amazon RDS is a distributed relational database service by Amazon.com. It is a web service running "in the cloud" and provides a relational database for use in applications. It is aimed at simplifying the set up, operation, and scaling a relational database. Complex administration processes like patching the database software, backing up databases and enabling point-in-time recovery are managed automatically. Scaling storage and compute resources can be performed by a single API call. Amazon RDS was first released on 22 October 2009 supporting MySQL databases . In June 2011, Oracle database support was added. On May 5, 2012, Microsoft SQL Server support was added.
Amazon RDS offers different features to support different use cases. Some of the major features are:
Multi AZ deployment 
Multi-Availability Zone deployments are targeted for production environments. Multi-AZ deployments aim to provide enhanced availability and data durability for MySQL instances. When a database instance is created or modified to run as a Multi-AZ deployment, Amazon RDS automatically provisions and maintains a synchronous “standby” replica in a different Availability Zone (independent infrastructure in a physically separate location). In the event of planned database maintenance or unplanned service disruption, Amazon RDS automatically fails over to the up-to-date standby, allowing database operations to resume without administrative intervention.
Multi AZ RDS instances are optional and have a cost associated with them. When creating your RDS instance, the user is asked if they would like to use a Multi-AZ RDS instance.
Read replicas 
Read Replicas use MySQL’s native, asynchronous replication functionality. Read Replicas are aimed at helping to scaling out beyond the capacity constraints of a single DB Instance for read-heavy database workloads. They can also be used for serving read traffic when the primary database is unavailable.
RDS Costs 
Amazon RDS instances are priced very similarly to Amazon Elastic Compute Cloud (EC2). RDS is charged per hour and come in two packages: On-Demand DB Instances and Reserved DB Instances. On-Demand instances are at an ongoing hourly usage rate. Reserved DB Instances require an up-front, one-time fee and in turn provide a discount on the hourly usage charge for that instance.
Apart from the hourly cost of running the RDS instance, users are charged for the amount of storage provisioned, data transfers and Input and Output operations performed. Due to the critical nature of databases, AWS have introduced Provisioned Input and Output Operations, in which the user can define how many IO per second is required by their application. Provisioned IOPS can be a big proportion of the total cost of running the RDS instance (RDS Provisioned IOPS: A Cost Analysis).
Database instance types 
Amazon RDS currently supports six DB Instance Classes, to support different types of workloads:
- Small DB Instance
- 1.7 GB memory, 1 ECU (1 virtual core with 1 ECU), 64-bit platform, Moderate I/O Capacity
- Large DB Instance
- 7.5 GB memory, 4 ECUs (2 virtual cores with 2 ECUs each), 64-bit platform, High I/O Capacity
- Extra Large DB Instance
- 15 GB of memory, 8 ECUs (4 virtual cores with 2 ECUs each), 64-bit platform, High I/O Capacity (MySQL DB Engine Only)
- High-Memory Extra Large Instance
- 17.1 GB memory, 6.5 ECU (2 virtual cores with 3.25 ECUs each), 64-bit platform, High I/O Capacity
- High-Memory Double Extra Large DB Instance
- 34 GB of memory, 13 ECUs (4 virtual cores with 3,25 ECUs each), 64-bit platform, High I/O Capacity
- High-Memory Quadruple Extra Large DB Instance
- 68 GB of memory, 26 ECUs (8 virtual cores with 3.25 ECUs each), 64-bit platform, High I/O Capacity
Competitors and alternatives 
Several other vendors provide cloud database services similar to Amazon RDS. Oracle offers Oracle Cloud, a database service supporting Oracle's database technology. Microsoft offers Windows Azure SQL, a service supporting the Microsoft SQL database. Competitors supporting MySQL include RackSpace Cloud Databases, Google Cloud SQL, HP Cloud for MySQL, Xeround Cloud Database and ClearDB.
- Amazon RDS APIs
- Availability Zone
- Reserved DB Instances
- Frequently Asked Question, Oracle Cloud, Retrieved 31-12-2012
- Data Management, Windows Azure, Retrieved 31-12-2012
- Learn how Cloud Databases delivers faster performance, RackSpace, Retrieved 31-12-2012
- About Google Cloud SQL, Google Developers, Retrieved 31-12-2012
- HP Cloud Relational Database for MySQL – FAQ, HP Cloud, Retrieved 31-12-2012
- FAQ – Xeround Cloud DBaaS, Xeround Cloud Database, Retrieved 31-12-2012
- Frequently Asked Questions, ClearDB, Retrieved 31-12-2012
- Amazon Relational Database Service - official homepage
- Getting Started with Amazon Relational Database Service (Amazon RDS) on YouTube
- RDS Provisioned IOPS: A Cost Analysis for High Performance Cloud Database