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Amazon RDS vs CosmosDB

Amazon RDS logo

Amazon RDS

Software

Set up, operate, and scale a relational database in the cloud

From
On request
Rated
-
Full reviewWebsite
CosmosDB logo

CosmosDB

Software

Globally distributed, multi-model database service from Azure

From
Free
Rated
-
Full reviewWebsite

The short version

  • Only CosmosDB has a free tier, so it costs nothing to try first.
  • Each has a real cost: Amazon RDS no super-user access or direct host connectivity limits advanced customization; CosmosDB autoscale provisioned throughput enforces a minimum of 1,000 RU/s, billed hourly whether or not the database is used
  • They diverge on capability: Amazon RDS covers Multiple DB Engines, CosmosDB covers Global Distribution.

Where they differ

Only the attributes on which Amazon RDS and CosmosDB actually diverge.

Attributes where Amazon RDS and CosmosDB differ
AttributeAmazon RDSCosmosDB
Starting priceOn requestFree
Pricing modelUnknownusage-based
Free tierNoYes
PlatformsAWS Cloud, Multi-AZ, Multi-regionWeb, Azure
Founded20061975

Identical on both: user rating (Not yet rated), category (Unknown).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Amazon RDS

  • Multiple DB Engines
  • Automated Backups
  • Multi-AZ Deployment
  • Read Replicas
  • Encryption
  • Performance Insights
  • Automatic Scaling
  • MySQL

Only in CosmosDB

  • Global Distribution
  • Multi-model APIs
  • Elastic Scaling
  • Five Consistency Levels
  • SLA-backed Latency
  • Automatic Indexing
  • Serverless
  • Azure Functions

Both cover

  • Web support

What people use each for

The jobs each tool is most often brought in to do.

Amazon RDS

  • Transaction processingnot CosmosDB
  • Data storagenot CosmosDB
  • Application backendnot CosmosDB
  • Reportingnot CosmosDB
  • Data analyticsnot CosmosDB

CosmosDB

  • Running a globally distributed multi model database on Azurenot Amazon RDS
  • Serving low latency reads and writes from multiple Azure regionsnot Amazon RDS
  • Storing document, key value and graph data behind a managed servicenot Amazon RDS

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Amazon RDS

  • No super-user access or direct host connectivity limits advanced customization
  • Pricing unpredictable and expensive compared to GCP alternatives with equivalent features
  • Limited access to system procedures and tables requiring advanced permissions
  • No Oracle RAC (Real Application Clusters) support for high-availability Oracle deployments

CosmosDB

  • Autoscale provisioned throughput enforces a minimum of 1,000 RU/s, billed hourly whether or not the database is used
  • Provisioned throughput is charged in every region the account is replicated to, so multi region accounts multiply the RU bill
  • Storage charges cover data, indexes and backups in each replicated region
  • Egress out of Azure and between regions is charged, though ingress is free
  • The free allowance is one account per Azure subscription, limited to 1,000 RU/s and 25 GB
  • RU/s rates vary by region and are only shown through the pricing calculator rather than a flat published rate

Pricing, plan by plan

Amazon RDS

On request

No published plan breakdown. See the Amazon RDS review.

CosmosDB

Free
  • Free TierFree
    • 1000 RU/s
    • 25GB storage
    • First 12 months
  • ServerlessFree
    • Pay per request
    • Auto-scaling
    • Event-driven workloads

Which should you pick?

Choose Amazon RDS if

  • You need multiple db engines.
  • You work on AWS Cloud, Multi-AZ, Multi-region.
  • You also want automated backups.
Amazon RDS review

Choose CosmosDB if

  • You need global distribution.
  • You want to start without paying.
  • You work on Web, Azure.
  • You also want multi-model apis.
CosmosDB review

Questions people ask

Is Amazon RDS or CosmosDB better?
Neither clearly leads. Amazon RDS starts at On request and CosmosDB at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Amazon RDS or CosmosDB?
CosmosDB has a free tier; the other does not. Paid plans start at On request for Amazon RDS and Free for CosmosDB.
Does Amazon RDS or CosmosDB run on more platforms?
Amazon RDS runs on AWS Cloud, Multi-AZ, Multi-region. CosmosDB runs on Web, Azure.
Can I use CosmosDB for free?
Yes. CosmosDB has a free tier, so you can try it without paying. Amazon RDS starts at On request.
What is Amazon RDS best used for?
Amazon RDS is most often used for transaction processing, data storage, application backend, reporting. Of those, transaction processing and data storage are not what CosmosDB is typically brought in for.
What can Amazon RDS do that CosmosDB cannot?
Amazon RDS covers Multiple DB Engines, Automated Backups, Multi-AZ Deployment, Read Replicas. CosmosDB covers Global Distribution, Multi-model APIs, Elastic Scaling, Five Consistency Levels. Both handle Web support.

Answered from the vendors’ own pages

Amazon RDS: What databases does Amazon RDS support?

Amazon RDS supports Amazon Aurora, PostgreSQL, MySQL, MariaDB, Oracle Database, and Microsoft SQL Server as managed database engines.

Source
Amazon RDS: Does Amazon RDS handle backups automatically?

Yes. Amazon RDS automates backup configuration, backing up your database and transaction logs. Blue/Green Deployments allow safer updates by mirroring production in staging before applying changes.

Source
Amazon RDS: How does Amazon RDS Proxy improve performance?

Amazon RDS Proxy is a managed database proxy that makes applications more scalable by reducing database connection overhead, more resilient to database failures, and more secure through built-in authentication.

Source
Amazon RDS: Does Amazon RDS provide read replicas?

Yes. Amazon RDS supports read replicas across availability zones and regions, enabling horizontal scaling of read capacity while maintaining a single write primary.

Source
Amazon RDS: Can I access the host directly via SSH or Remote Desktop?

No. Amazon RDS does not allow direct host access via SSH, Telnet, or Windows Remote Desktop Connection. Database access is limited to database clients and management console.

Source
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