You’ve decided to move your applications from on-premises to AWS and are looking at the cloud services that best meet your needs. When moving an application with a relational database like Oracle, MySQL, or SQL Server to the cloud, you'll face the choice between Amazon RDS and AWS EC2.

You need to decide whether to:

Use AWS’s Relational Database Service (RDS)
Host a database server on an AWS EC2 (Elastic Compute) instance

What is AWS RDS?

Amazon Relational Database Service (Amazon RDS) is a managed Database-as-a-Service (DBaaS) that helps IT administrators easily set up, run, and scale relational databases in the cloud. RDS supports popular database engines like MySQL, MariaDB, PostgreSQL, Oracle, and Microsoft SQL Server.

When moving to the cloud, most applications using these databases can switch to Amazon RDS without much hassle. You can choose different database instance types based on your needs for CPU, memory, storage, and networking. With Amazon RDS, Amazon takes care of tasks like provisioning, setup, patching, backup, recovery, and failure repair, saving your team from these time-consuming tasks.

Amazon RDS automatically backs up your databases every 24 hours, ensuring that in the worst case, you can recover data for up to 24 hours. With a multi-region active-active strategy, you can achieve near-zero data loss and minimal recovery time. Routine patching is also automated with set maintenance windows for security. On top of this it also supports PITR recovery so you can get back your database to any particular timestamp in last 7 days.

RDS allows you to have read replicas in zones closer to your users, which increases read capacity and reduces the load on production servers by routing read queries to the replicas. You can also send heavy queries to read replicas to lessen the burden on your main servers.

What is Amazon EC2?

Amazon Elastic Compute Cloud (EC2) is a web service that gives you secure access to server instances when you need them. It's easy to get and set up capacity – just use the Amazon EC2 web service interface to add capacity as needed.

You have full control over your computing resources and can scale up or down based on your needs. To provide database services for your application, you can set up EC2 instances and install the necessary database engines yourself.

Next, let’s look at the pros and cons of choosing between Amazon RDS and EC2 for your database.

Administration

When it comes to administration, Amazon RDS is easy to set up because AWS automates the entire process of management, maintenance, and security, allowing you to focus on essential tasks instead of routine maintenance. You can access its capabilities through the AWS Management Console, AWS RDS command-line interface, or simple REST API calls.

AWS EC2 gives you full control over the OS, database version, configuration, and other software components, but you are responsible for all routine maintenance activities, including patches, upgrades, backups, replication, and clustering.

High Availability

Amazon RDS has built-in high availability. It automatically creates a primary database instance and replicates the data to a standby instance in a different Amazon Availability Zone. This ensures that if there is an outage in one zone, you can recover your database from the other zone.

On the other hand, with AWS EC2, you are responsible for configuring the database server in a highly available cluster.

Backups

With Amazon RDS, you can set up automated backups. AWS CloudWatch can notify you about backup failures, completions, and more. You can also get database snapshots on-demand and keep them as long as you need.

With AWS EC2, you have to enable backups yourself and set up separate monitoring to ensure regular backups. You cannot use AWS CloudWatch for this.

Scalability

Amazon RDS easily integrates with Amazon’s scaling tools for both vertical and horizontal scaling. You can scale up to a larger instance in a few clicks, and you can automate the creation of additional read replicas to handle increased read-only workloads.

With AWS EC2, you have to set up a scalable architecture manually, which includes setting up multiple EC2 instances, load balancing, configuring Availability Groups, and Sharding.

Performance

With Amazon RDS, you can configure your instance with a specific number of provisioned IOPS for fast and consistent performance, though it can be expensive. RDS integrates with Amazon CloudWatch for monitoring database performance.

With AWS EC2, you need to choose the right storage volume for the IOPS and latency you need. Since the database server is not AWS-managed, you cannot use AWS CloudWatch for performance monitoring and need to use third-party tools instead.

Storage

With Amazon RDS, you have three storage options:

General-purpose SSD: Cost-effective, delivers single-digit millisecond latencies, and handles up to 3,000 IOPS.
Provisioned IOPS: Ideal for database-intensive workloads needing low latency and very high IOPS throughput.
Magnetic: Supports magnetic storage for backward compatibility.
With AWS EC2, the IOPS and latency depend on the instance type. You can get up to 16,000 IOPS and 2,000 Mbps with the right EBS-optimized instance.

Support and Control

With Amazon RDS, you are limited to the database engines and versions supported by Amazon. Amazon manages upgrades and patches, so you don't handle the database server directly. You have access to database administration tools for necessary tasks.

With AWS EC2, you can install any database engine and version you want, without being limited by AWS's RDS support. You have full control over the operating system and the database server. You can apply updates and patches, set maintenance windows, run multiple instances on the same EC2 instance, and control the ports used.

Security

Amazon RDS offers encryption both at rest and in transit. This means the storage for database instances, read replicas, automated backups, and snapshots are all encrypted while stored.

In AWS EC2, encryption is handled at the EBS volume level, and you can also configure encryption at the database level.

Licensing

Amazon RDS offers both “License Included” and “Bring-Your-Own-License (BYOL)” models, depending on the database engine.

For example, Oracle RDS allows you to bring your license, but Amazon RDS for SQL Server only supports the “License Included” model. You cannot bring your SQL licenses to RDS, as SQL Server is licensed through AWS.

With AWS EC2, you can bring your database licenses regardless of the database engine.

Cost

Spending depends on the instance type, and you can use the AWS Cost Calculator to get detailed costs.

Amazon RDS:

Usually more expensive because Amazon handles routine management tasks for you.

AWS EC2:

Generally cheaper since you manage the database server yourself.
You are responsible for tasks like backup, recovery, patching, and load management.

How to Choose Between AWS RDS and Amazon EC2

Choosing between a database on an EC2 instance and RDS means deciding between managing everything yourself and using a managed service where AWS handles routine tasks. With RDS, a simple API call gives you control over deployment, backups, snapshots, restores, sizing, high availability, and replicas.

In contrast, using EC2 means you need to manually set up, configure, manage, and tune components like EC2 instances, storage, scalability, networking, and security.

Using RDS reduces management overhead and increases flexibility and automation. You can use automated CI/CD systems with AWS CLI, CDK, and CloudFormation to deploy the database with minimal manual work. Managed services let you control the infrastructure and design services that are easy to deploy, replicate, and have auto-healing features.

However, cost is a key factor. Amazon RDS can be slightly more expensive than EC2 for the same configuration. If you have a tight budget or need a database engine or version not supported by RDS, you might have to use an EC2-hosted database.

At KuebOps Consulting, we highly recommend using RDS instances over EC2 for database to our clients. The additional cost that you pay almost always saves a lot more money than what you would spend on managing and scaling the database yourself on an EC2 instance.

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