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Databases · head to head

Cassandra vs OpenAI API

Cassandra logo

Cassandra

Databases

Manage massive amounts of data with linear scalability

From
Free
Free plan
Yes
Visit CassandraFull review
OpenAI API logo

OpenAI API

Machine Learning

Hosted API for OpenAI's language, embedding, image and audio models, billed per token

From
$0.15/per-million-tokens
Free plan
No
Visit OpenAI APIFull review

The short version

  • Cassandra is free; OpenAI API starts at $0.15/mo.
  • Only Cassandra lists linear Scalability; only OpenAI API lists text and reasoning models.
  • Where Cassandra falls short: no support for joins across tables.
  • Prices and features on this page were last checked on 13 November 2026.

Where they differ

Only the attributes on which Cassandra and OpenAI API actually diverge.

Attributes where Cassandra and OpenAI API differ
AttributeCassandraOpenAI API
Starting priceFree$0.15/per-million-tokens
Free tierYesNo
PlatformsLinux, macOS, Windows, Self-hostedAPI
CategoryDatabasesMachine Learning
Founded20082015

Not yet recorded: pricing model for Cassandra.

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 Cassandra

  • Linear Scalability
  • Fault Tolerance
  • Multi-datacenter Replication
  • Tunable Consistency
  • CQL Query Language
  • Distributed Architecture
  • No Single Point of Failure
  • DataStax

Only in OpenAI API

  • Text and reasoning models
  • Embeddings
  • Speech and audio
  • Image generation
  • Function calling
  • Structured outputs
  • Batch processing
  • Prompt caching

What people use each for

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

Cassandra

  • Real-time applicationsnot OpenAI API
  • Content managementnot OpenAI API
  • User profilesnot OpenAI API
  • Mobile backendsnot OpenAI API
  • Cachingnot OpenAI API

OpenAI API

  • Adding summarisation, drafting or classification to an existing product where building a model would take longer than the product's whole roadmapnot Cassandra
  • Retrieval-augmented question answering over internal documents, using the embedding and generation models togethernot Cassandra
  • Extracting structured records from unstructured text, where schema-constrained output removes most of the parsing problemnot Cassandra
  • Prototyping a language feature quickly to find out whether it is worth the cost of a self-hosted alternative laternot Cassandra

Where each one falls short

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

Cassandra

  • No support for joins across tables
  • No ACID transactions across multiple rows
  • Data model must be designed around query patterns upfront, making schema evolution difficult
  • Partition key misconfigurations can cause uneven data distribution and hotspots that degrade performance

OpenAI API

  • Cost scales with tokens rather than with seats, so a successful feature's bill grows with its adoption, and an interface that lets users paste long documents has no natural ceiling on spend unless you build one yourself
  • Models are deprecated on the vendor's timetable, and a fine-tuned model built on a retired base goes with it, so the tuning work and the data curation behind it must be redone rather than migrated
  • Behaviour shifts between model versions in ways no test catches unless you wrote one, so prompts tuned over months against a particular snapshot can regress quietly on migration, which makes an evaluation suite a prerequisite rather than an improvement
  • It cannot run inside your own network, so data residency requirements, air-gapped environments and contracts forbidding third-party processing rule it out regardless of the provider's own security posture
  • You inherit its availability and its rate limits, so a provider incident is an outage in your product and a traffic spike can be throttled at precisely the moment the feature is proving itself

Pricing, plan by plan

Cassandra

Free

No published plan breakdown. See the Cassandra review.

OpenAI API

$0.15/per-million-tokens
  • GPT-4o mini$0.15
    • Fast
    • Affordable
  • GPT-4o$5
    • Multimodal
    • 128K context

Which should you pick?

Choose Cassandra if

  • You need linear scalability.
  • You want to start without paying.
  • You work on Linux, macOS, Windows, Self-hosted.
  • You also want fault tolerance.
Cassandra review

Choose OpenAI API if

  • You need text and reasoning models.
  • You work on API.
  • You also want embeddings.
OpenAI API review

Questions people ask

Is Cassandra or OpenAI API better?
Neither clearly leads. Cassandra starts at Free and OpenAI API at $0.15/per-million-tokens, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Cassandra or OpenAI API?
Cassandra has a free tier; the other does not. Paid plans start at Free for Cassandra and $0.15/per-million-tokens for OpenAI API.
Does Cassandra or OpenAI API run on more platforms?
Cassandra runs on Linux, macOS, Windows, Self-hosted. OpenAI API runs on API.
Can I use Cassandra for free?
Yes. Cassandra has a free tier, so you can try it without paying. OpenAI API starts at $0.15/per-million-tokens.
What is Cassandra best used for?
Cassandra is most often used for real-time applications, content management, user profiles, mobile backends. Of those, real-time applications and content management are not what OpenAI API is typically brought in for.
What can Cassandra do that OpenAI API cannot?
Cassandra covers Linear Scalability, Fault Tolerance, Multi-datacenter Replication, Tunable Consistency. OpenAI API covers Text and reasoning models, Embeddings, Speech and audio, Image generation.

Answered from the vendors’ own pages

Cassandra: Does Cassandra support joins between tables?

No. Cassandra does not support joins or foreign keys. The data model requires denormalization, meaning data must be duplicated across tables to support different query patterns.

Source
OpenAI API: Is my data used to train the models?

API inputs and outputs are not used for training by default, which differs from the consumer product. Retention periods and enterprise terms change, so read the current data usage policy rather than trusting a summary.

Cassandra: Does Cassandra offer ACID transactions?

No. Cassandra provides only row-level atomicity and isolation, not full ACID transactions across multiple rows or tables. It uses lightweight transactions via Paxos for per-row compare-and-set operations.

Source
OpenAI API: Can I run these models on my own hardware?

No. The weights are not distributed. If self-hosting is a requirement, you are looking at open-weight models instead, with the operational and quality trade-offs that implies.

Cassandra: What programming languages can connect to Cassandra?

Cassandra supports official drivers for multiple languages including Python, Java, Node.js, and Go, allowing applications to communicate via the native Cassandra protocol.

Source
OpenAI API: How is it priced?

Per token, with input and output priced differently and each model priced differently. Batch processing and cached input prefixes reduce it. The practical consequence is that your bill is a function of prompt design, not just of request count.

Cassandra: Can I deploy Cassandra in the cloud?

Yes. Cassandra can run on any cloud platform (AWS, Google Cloud, Azure) via Docker, virtual machines, or managed services like DataStax Astra DB, which provides a fully managed DBaaS option.

Source
OpenAI API: What is the difference from Azure OpenAI Service?

The same model family delivered by Microsoft under an Azure contract, with Azure identity, networking and regional controls, and a different release cadence for new models. Enterprises with an Azure agreement often choose it for procurement and data residency reasons rather than technical ones.

Cassandra: Does Cassandra have a free option?

The open source Apache Cassandra is free. DataStax also offers Astra DB with a free tier providing up to 25GB storage and 25 million read/write operations per month.

Source
OpenAI API: How do I keep the cost under control?

Cap input length, cache repeated prefixes, route easy requests to smaller models, use the batch path where latency does not matter, and set per-user limits before launch rather than after the first surprising invoice.

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