- Amazon RDS runs six relational engines as a managed service: IBM Db2, MariaDB, Microsoft SQL Server, MySQL, Oracle Database and PostgreSQL. Aurora is a separate, related service.
- AWS handles provisioning, patching, backups, failure detection and recovery; you remain responsible for query tuning and database design.
- You pay per instance-hour plus storage, backup storage above a free allowance and data transfer; a small PostgreSQL instance lists at 0.016 USD per hour in US East (N. Virginia).
- High availability comes from Multi-AZ deployments; read scaling from up to 15 read replicas; recovery from automated backups (up to 35 days) and snapshots.
- Default quotas include 40 DB instances per Region and storage up to 64 TiB per instance; there is no operating system access except through RDS Custom.
What is AWS RDS (Amazon Relational Database Service)?
AWS RDS is a managed relational database service. The Amazon RDS User Guide says RDS manages backups, software patching, automatic failure detection and recovery. The basic unit is the DB instance, an isolated database environment that can hold one or more databases, which you create and modify through the console, the AWS CLI or the RDS API and connect to with the same tools you would use for a standalone server.
The User Guide compares three models. On premises you manage everything. On Amazon EC2, AWS manages the hardware but you still install, patch, back up and fail over the database yourself. On RDS, AWS takes over scaling, high availability, backups, engine and operating system patching and installation, while you keep application optimisation. AWS recommends RDS as the default choice for most relational deployments, but the shared responsibility model is explicit that query tuning remains yours.
| Task | Database on Amazon EC2 | Amazon RDS |
|---|---|---|
| Application and query optimisation | You | You |
| Scaling, high availability, backups | You | AWS |
| Database software install and patching | You | AWS |
| Operating system install and patching | You | AWS |
| Server maintenance, hardware, power and network | AWS | AWS |
RDS database engines
RDS supports six engines. Features and versions vary by engine and Region, and each engine has its own pricing page and licensing model. Aurora (MySQL- and PostgreSQL-compatible, plus Aurora DSQL) is sold under the RDS family but uses a different storage architecture; see the Aurora guide in the related links.
| Engine | Licensing on RDS | Notes |
|---|---|---|
| PostgreSQL | Open source, no licence fee | Supports Multi-AZ DB clusters with two readable standbys |
| MySQL | Open source, no licence fee | Supports Multi-AZ DB clusters with two readable standbys |
| MariaDB | Open source, no licence fee | Free tier eligible, like PostgreSQL and MySQL |
| Microsoft SQL Server | Licence included (Express, Web, Standard, Enterprise); bring your own media is also available | Express Edition is the only free tier edition |
| Oracle Database | Licence included or bring your own licence | Up to 15 read replicas, AWS recommends 5 |
| IBM Db2 | Bring your own licence or licence through AWS Marketplace | Not free tier eligible |
Instance classes and storage
A DB instance class sets CPU and memory. RDS groups classes into general purpose (db.m*), memory optimised (db.r*, db.x*, db.z*), compute optimised (db.c*) and burstable (db.t*), with AWS Graviton processors indicated by the "g" in names such as db.m7g and db.m8g. You can change the class later by modifying the instance.
Storage is Amazon EBS: General Purpose SSD (gp3 and gp2) for most workloads, or Provisioned IOPS SSD (io1, io2) for I/O-intensive production databases. The pricing page lists General Purpose capacity from 20 GiB to 64 TiB. Magnetic storage is deprecated: it is no longer offered for new instances, and from 1 July 2026 snapshots can no longer be restored to it.
High availability, read replicas and backups
Multi-AZ. A Multi-AZ DB instance deployment keeps a synchronous standby in a second Availability Zone that RDS fails over to automatically; a Multi-AZ DB cluster (PostgreSQL and MySQL) adds two readable standbys in three AZs. Read replicas are asynchronous, read-only copies for scaling reads or disaster recovery, including in other Regions. The differences and costs are in RDS Multi-AZ vs read replicas.
Backups. Automated backups allow point-in-time recovery within a retention period of up to 35 days, and manual snapshots are kept until you delete them. Every restore creates a new instance; the steps are in RDS backups and snapshots.
Connections. For applications that open many short-lived connections, such as Lambda functions, RDS Proxy pools connections and shortens failover.
AWS RDS pricing and free tier in brief
RDS has no minimum fee. You pay for instance hours (billed per second after a 10-minute minimum), provisioned storage, backup storage above the free allowance, data transfer and optional features. Multi-AZ roughly doubles instance and storage cost. Reserved Instances and Database Savings Plans reduce the instance rate in return for a commitment. Full details and three worked examples are in AWS RDS pricing.
New AWS accounts now get credits rather than 12 months of free instance hours: 100 USD on sign-up and up to 100 USD more, usable on RDS micro instances among other services. Older accounts keep the legacy 750-hour offer until their 12 months end. See the RDS free tier guide.
RDS limits and quotas
Quotas apply per account and per Region. Most can be raised through Service Quotas; the table lists the defaults documented in the RDS User Guide.
| Limit | Default | Notes |
|---|---|---|
| DB instances per Region | 40 | Shared with Aurora, Neptune and DocumentDB instances; adjustable |
| Read replicas per primary | 15 | Adjustable for RDS |
| Manual DB snapshots per Region | 100 | Automated backups do not count |
| Total storage for all DB instances per Region | 100,000 GB | Adjustable |
| Storage per instance (General Purpose or Provisioned IOPS) | Up to 64 TiB | Minimum 20 GiB for General Purpose |
| Backup retention | 0 to 35 days | Manual snapshots never expire |
| Reserved DB instances per Region | 40 | Adjustable |
| RDS Proxy proxies per Region | 20 | Adjustable |
| Stopping an instance | Up to 7 consecutive days | Restarts automatically afterwards |
When to choose RDS, and when not to
RDS suits teams that want a standard PostgreSQL, MySQL, MariaDB, SQL Server, Oracle or Db2 database without running servers, with predictable instance-based pricing and AWS-managed backups and failover.
Look elsewhere when:
- You need operating system access or custom engine patches: AWS documents that RDS does not allow direct host access by Telnet or SSH. RDS Custom covers some of these cases for SQL Server, but AWS has announced end of support for RDS Custom for Oracle on 31 March 2027.
- You want storage that grows automatically across AZs, more replicas or serverless scaling: compare Amazon RDS vs Amazon Aurora.
- Your data is key-value, document or graph shaped: see AWS database services compared.
- You want branching and scale to zero for many small Postgres databases: see Neon vs AWS RDS or Supabase vs AWS RDS.
- You are weighing clouds: AWS RDS vs Azure SQL Database and AWS RDS vs Google Cloud SQL.
Pricing
Prices from the provider's official pricing pages, checked 8 October 2026, region US East (N. Virginia), in USD, excluding tax. List prices only; discounts, commitments and your actual usage change the bill.
Headline RDS for PostgreSQL On-Demand rates: db.t4g.micro 0.016 USD per hour and db.m8g.large 0.168 USD per hour (Single-AZ), and gp3 storage 0.115 USD per GB-month. That puts a micro instance with 20 GB at about 13.98 USD a month (730 hours x 0.016 + 20 x 0.115) before tax and data transfer. Other engines, licence-included editions and Regions differ; see AWS RDS pricing for the breakdown.
Frequently asked questions
What is RDS in AWS?
Amazon RDS (Relational Database Service) is AWS's managed service for relational databases. It runs PostgreSQL, MySQL, MariaDB, SQL Server, Oracle and Db2 on instances that AWS provisions, patches, backs up and fails over for you.
Is Amazon RDS the same as Aurora?
No. Aurora is part of the RDS family and uses the same console and APIs, but it is a separate engine family (MySQL- and PostgreSQL-compatible) with its own distributed storage and pricing. The RDS User Guide covers engines other than Aurora.
Is AWS RDS a database or a service?
A service. RDS runs existing database engines for you; the database itself is PostgreSQL, MySQL or one of the other supported engines, so standard drivers and tools connect to it.
Can I access the server behind an RDS instance?
No, RDS does not give operating system access. If an application needs OS-level customisation, AWS offers RDS Custom (for SQL Server; RDS Custom for Oracle reaches end of support on 31 March 2027) or you can run the database on EC2.
How much does Amazon RDS cost?
In US East (N. Virginia) a db.t4g.micro PostgreSQL instance lists at 0.016 USD per hour and gp3 storage at 0.115 USD per GB-month (October 2026), so a small database starts at roughly 14 USD a month. Production instances with Multi-AZ typically cost hundreds of dollars a month.
What is the maximum storage for an RDS instance?
64 TiB for General Purpose SSD and Provisioned IOPS SSD storage, according to the RDS pricing page. Aurora has a separate limit.
Sources
- Amazon RDS
- Amazon RDS User Guide: What is Amazon RDS?
- AWS Free Tier
- Amazon RDS User Guide: Quotas and constraints
- Amazon RDS User Guide: DB instance classes
- Amazon RDS User Guide: Backup retention period
- Amazon RDS User Guide: Stopping a DB instance
- Amazon RDS User Guide: Restoring from a DB snapshot
- Amazon RDS pricing
- Amazon RDS FAQs
- Amazon RDS Multi-AZ
- Amazon RDS Custom
- Amazon RDS User Guide: Amazon RDS for PostgreSQL
- Amazon RDS Reserved Instances
- AWS decision guide: Choosing an AWS database service
- AWS price data: RDS for PostgreSQL RIs (includes On-Demand rates), US East (N. Virginia)
- AWS price data: RDS for PostgreSQL On-Demand (all Regions)
Checked 8 October 2026.
How we research cloud database guides: our editorial method. CodeWithSQL earns nothing from the providers mentioned.