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Databases · head to head

CosmosDB vs IBM Db2

CosmosDB logo

CosmosDB

Databases

Globally distributed, multi-model database service from Azure

From
Free
Rated
-
Full reviewWebsite
IBM Db2 logo

IBM Db2

Databases

The AI-powered database built for demanding enterprise workloads

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: CosmosDB autoscale provisioned throughput enforces a minimum of 1,000 RU/s, billed hourly whether or not the database is used; IBM Db2 cloud-based Db2 is newer than mainframe version; some legacy mainframe features not yet available in cloud
  • They diverge on capability: CosmosDB covers Global Distribution, IBM Db2 covers AI-powered Query Optimization.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which CosmosDB and IBM Db2 actually diverge.

Attributes where CosmosDB and IBM Db2 differ
AttributeCosmosDBIBM Db2
Pricing modelusage-basedUnknown
PlatformsWeb, AzureIBM Cloud, On-premises (mainframe), Linux, UNIX
Founded19751983

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated), category (Databases).

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 CosmosDB

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

Only in IBM Db2

  • AI-powered Query Optimization
  • Data Virtualization
  • Advanced Compression
  • pureScale Clustering
  • BLU Acceleration
  • Workload Management
  • Federated Queries
  • IBM Cloud

What people use each for

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

CosmosDB

  • Running a globally distributed multi model database on Azurenot IBM Db2
  • Serving low latency reads and writes from multiple Azure regionsnot IBM Db2
  • Storing document, key value and graph data behind a managed servicenot IBM Db2

IBM Db2

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

Where each one falls short

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

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

IBM Db2

  • Cloud-based Db2 is newer than mainframe version; some legacy mainframe features not yet available in cloud
  • Pricing complexity with hourly billing for compute and storage can result in unpredictable costs
  • Less community support and documentation compared to open-source alternatives like PostgreSQL
  • Requires IBM expertise and tools for optimal configuration and tuning
  • Migration from mainframe Db2 to cloud Db2 requires careful planning and testing

Pricing, plan by plan

CosmosDB

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

IBM Db2

Free
  • Free TierFree
    • Entry-level exploration
    • Limited resources
  • Standard$99/month
    • Production-ready workloads
    • Shared computing resources
  • Enterprise$969/month
    • Dedicated computing resources
    • Enhanced capabilities

Which should you pick?

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

Choose IBM Db2 if

  • You need ai-powered query optimization.
  • You want to start without paying.
  • You work on IBM Cloud, On-premises (mainframe), Linux, UNIX.
  • You also want data virtualization.
IBM Db2 review

Questions people ask

Is CosmosDB or IBM Db2 better?
Neither clearly leads. CosmosDB starts at Free and IBM Db2 at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, CosmosDB or IBM Db2?
CosmosDB starts at Free and IBM Db2 at Free.
Does CosmosDB or IBM Db2 run on more platforms?
CosmosDB runs on Web, Azure. IBM Db2 runs on IBM Cloud, On-premises (mainframe), Linux, UNIX.
Can I use CosmosDB for free?
Both have a free tier, so you can try either at no cost before committing.
What is CosmosDB best used for?
CosmosDB is most often used for running a globally distributed multi model database on azure, serving low latency reads and writes from multiple azure regions, storing document, key value and graph data behind a managed service. Of those, running a globally distributed multi model database on azure and serving low latency reads and writes from multiple azure regions are not what IBM Db2 is typically brought in for.
What can CosmosDB do that IBM Db2 cannot?
CosmosDB covers Global Distribution, Multi-model APIs, Elastic Scaling, Five Consistency Levels. IBM Db2 covers AI-powered Query Optimization, Data Virtualization, Advanced Compression, pureScale Clustering.

Answered from the vendors’ own pages

CosmosDB: Is there a free tier for Azure Cosmos DB?

Yes, Cosmos DB offers a free tier with 1,000 RU/s of throughput and 25 GB of storage per month for the lifetime of the account, available to new accounts.

Source
IBM Db2: What is IBM Db2?

IBM Db2 is a cloud-based relational database management system designed for enterprise data management. It evolved from IBM's research into relational databases in the 1970s and launched for mainframe systems in 1983.

Source
CosmosDB: How is Cosmos DB priced after the free tier?

Cosmos DB uses three billing models: provisioned throughput billed per request unit per second, vCore pricing for certain APIs, or serverless consumption pricing where you pay only for requests processed. Reserved capacity offers 20% discount for one year or 30% for three years.

Source
IBM Db2: What are the pricing tiers for IBM Db2 cloud database?

IBM Db2 offers a perpetually free tier for exploration, Standard tier starting at $99/month (billed hourly), and Enterprise tier starting at $969/month (billed hourly). Storage costs $0.000282 per GB per hour across tiers.

Source
CosmosDB: Can I change my pricing model after choosing one?

No. Once you select a compute pricing model and API, they cannot be changed. This choice is permanent for that database.

Source
IBM Db2: Does Db2 support automatic failover and disaster recovery?

Yes. Db2 includes HADR (High Availability Disaster Recovery) with multizone region support, point-in-time recovery, built-in self-service snapshots, and geo-replicated data recovery backups.

Source
CosmosDB: Is there a trial period for Cosmos DB beyond the free tier?

Azure offers a 30-day free trial account for all Azure services. Additionally, Azure AI customers may be eligible for a 90-day free Cosmos DB subscription through the Azure AI Advantage program.

Source
IBM Db2: Can Db2 scale horizontally?

Yes. Db2 supports both vertical and horizontal scaling through its pureScale architecture, allowing it to handle growing data volumes while maintaining performance for mission-critical applications.

Source
IBM Db2: How long has DB2 been in production?

DB2 launched in June 1983 on the MVS operating system and has operated for over 40 years. It remains the foundational database for the largest enterprises globally, managing data for financial, retail, healthcare, and insurance institutions.

Source
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