Softwr

Databases · head to head

CosmosDB vs Postgres

CosmosDB logo

CosmosDB

Databases

Globally distributed, multi-model database service from Azure

From
Free
Rated
-
Full reviewWebsite
Postgres logo

Postgres

Technology

The world's most advanced open source database

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; Postgres each major version is supported for only 5 years after its initial release, after which it is end-of-life
  • They diverge on capability: CosmosDB covers Global Distribution, Postgres covers ACID compliance.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which CosmosDB and Postgres actually diverge.

Attributes where CosmosDB and Postgres differ
AttributeCosmosDBPostgres
Pricing modelusage-basedopen-source
PlatformsWeb, AzureLinux, Windows, Macos, Docker
CategoryDatabasesTechnology
Founded19751996

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

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 Postgres

  • ACID compliance
  • Complex queries
  • Foreign keys
  • Triggers
  • Views
  • Stored procedures
  • JSON/JSONB support
  • Full-text search

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 Postgres
  • Serving low latency reads and writes from multiple Azure regionsnot Postgres
  • Storing document, key value and graph data behind a managed servicenot Postgres

Postgres

  • Running a general purpose relational database for applicationsnot CosmosDB
  • Self-hosting an open source SQL database with no licence feenot CosmosDB
  • Workloads needing extensions, JSON and full text search in one enginenot 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

Postgres

  • Each major version is supported for only 5 years after its initial release, after which it is end-of-life
  • Major version upgrades break on-disk compatibility and require a full dump and reload or the pg_upgrade tool
  • New major versions ship about once a year, so staying supported means a disruptive upgrade cycle
  • Minor releases contain only frequently-encountered bug fixes, low-risk fixes, security issues and data corruption fixes, so feature gaps are not addressed within a major version
  • There is no vendor SLA; commercial support must be bought separately from third party professional services listed by the project

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

Postgres

Free
  • Community EditionFree
    • Full database features
    • No limitations
    • Community support

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 Postgres if

  • You need acid compliance.
  • You want to start without paying.
  • You work on Linux, Windows, Macos, Docker.
  • You also want complex queries.
Postgres review

Questions people ask

Is CosmosDB or Postgres better?
Neither clearly leads. CosmosDB starts at Free and Postgres at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, CosmosDB or Postgres?
CosmosDB starts at Free and Postgres at Free.
Does CosmosDB or Postgres run on more platforms?
CosmosDB runs on Web, Azure. Postgres runs on Linux, Windows, Macos, Docker.
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 Postgres is typically brought in for.
What can CosmosDB do that Postgres cannot?
CosmosDB covers Global Distribution, Multi-model APIs, Elastic Scaling, Five Consistency Levels. Postgres covers ACID compliance, Complex queries, Foreign keys, Triggers.

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
Postgres: How much does PostgreSQL cost to use?

PostgreSQL is completely free to download, install, and use. No licensing fees, subscription costs, or per-seat charges apply. The database is open source under the PostgreSQL License. Source: https://www.postgresql.org

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
Postgres: Are there commercial PostgreSQL support options available?

Official PostgreSQL (the project) is free. Commercial PostgreSQL services such as hosting, professional support, training, and managed database services are offered by third-party vendors, not the PostgreSQL project itself. Source: https://www.postgresql.org

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
Postgres: Do I need a license to use PostgreSQL commercially?

No. PostgreSQL is open source under the PostgreSQL License, which permits free commercial use without royalties, licensing fees, or support obligations. Source: https://www.postgresql.org

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
Share

Related pages

More on CosmosDB

More on Postgres

Keep looking

Other head to heads