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It's a split decision.
Choose Apache Cassandra if your application needs a distributed database that scales across nodes and data centers, and your team can operate its own infrastructure. Choose MongoDB if you want a document model and the option to use managed Atlas, with search, analytics and vector capabilities in its platform. Cassandra is free to self-host under Apache License 2.0; MongoDB Atlas has a capped free tier and paid plans that scale with compute and usage.
01Side by side
| Apache Cassandra | MongoDB | |
|---|---|---|
| Pricing model | Free software; teams pay for their infrastructure | Atlas hourly billing; paid tiers scale with usage |
| Free tier | Free to download and self-host | M0: 512 MB, 32 MB sort memory, 100 ops/sec |
| Open source and licence | Open source under Apache License 2.0 | Community Edition is free; Enterprise uses a commercial license |
| Self-hosting | Run on commodity hardware, cloud, or on-premises | Self-managed software is available for your infrastructure |
| API and SDKs | CQL is referenced; language SDKs aren't enumerated | Single query API; language SDKs aren't enumerated |
| CLI and docs | Homepage links a Cassandra 5.0 Quickstart | Documentation, community forums, and MongoDB University |
| Integrations | Community ecosystem; Kafka and object storage are mentioned | Integrations with 100+ technologies |
| Limits and scaling | Linear throughput scaling; add nodes online | M0 caps operations; dedicated tiers list compute and storage |
Apache Cassandra Choose Apache Cassandra if
- Choose Apache Cassandra if you need linear scale-out across nodes.
- Choose Apache Cassandra if your team can operate the cluster.
- Choose Apache Cassandra if Apache License 2.0 matters.
MongoDB Choose MongoDB if
- Choose MongoDB if you want a managed Atlas deployment option.
- Choose MongoDB if your app suits a flexible document model.
- Choose MongoDB if you need Atlas search or vector capabilities.
02Pricing at real usage
Cassandra is free to download and self-host under Apache License 2.0. The software has no published monthly or annual charge; teams need to budget separately for the infrastructure they run. MongoDB Atlas M0 is free forever, with 512 MB of storage, 32 MB of sort memory and up to 100 operations per second. For development and testing, Flex lists a $0.011/hour base rate, 5 GB of storage and usage costs of $8–$30 per month. Dedicated clusters start at $56.94/month, with hourly rates rising across larger tiers. Atlas bills clusters hourly and sends monthly invoices; the pricing page lists no annual billing option. At higher usage, compute, storage and other charges can increase the bill. Atlas Infinite lists $0.09/hour and is in public preview.
03API, SDKs and integration
MongoDB describes a document model with a single query API for application data. Atlas adds database search, vector search, stream processing and analytics capabilities. Its site also lists integrations with 100+ technologies. The Cassandra homepage links a Cassandra 5.0 Quickstart, and community material references CQL and projects, tools, products and services around Cassandra. It also mentions Kafka and object storage in a community talk. The product pages do not enumerate supported SDK languages or a first-party CLI for either database, so verify language support and command-line workflows in the current developer docs before planning an integration. MongoDB links documentation, community forums and MongoDB University; Cassandra links its Quickstart and community resources. Both require checking the relevant driver and tool versions against your application stack.
04Open source, self-hosting and lock-in
Cassandra is open source under Apache License 2.0 and can run on commodity hardware, cloud infrastructure or on-premises systems. Its masterless design and replication options give operators control over cluster placement and data-center resilience, while leaving operations to the team. MongoDB offers self-managed software, including a Community Edition for local development at no cost, as well as commercial Enterprise Advanced. Atlas is the managed option. MongoDB also lists Relational Migrator, a tool for migrating to MongoDB; Cassandra community material includes a talk on efficient export. Those references do not establish compatible export formats or a complete exit process. Check which data formats, indexes and application queries you can move, and what migration work your schemas and workloads require, before committing to either platform.
Questions people ask
Who is MongoDB's biggest competitor?
There is no single biggest competitor for every MongoDB workload. Apache Cassandra is an alternative when a team needs a distributed database built for high availability and scale-out. MongoDB instead centers on a document model and offers Atlas services for search, analytics, stream processing and AI applications.
Is Apache Cassandra still used?
Cassandra remains an active Apache project: its homepage links a Cassandra 5.0 Quickstart and community talks published in 2025. Its stated fit is large-scale data with high availability, replication across data centers and linear scalability. Whether it fits a particular system depends on its workload and the team's ability to operate the cluster.
Is MongoDB still relevant in 2026?
MongoDB's current product lineup includes Atlas, self-managed deployments, a document database, search, vector search, stream processing and analytics. Those capabilities suit teams building applications around a document model or using Atlas services. Evaluate the specific service, limits and price against your workload rather than choosing on broad relevance alone.
Is MongoDB a NoSQL database?
Yes. MongoDB is a document database, a type of NoSQL database. Its document model is designed for application data, and MongoDB describes a single query API for that data. It is distinct from Cassandra, which is a distributed NoSQL database designed for scalability and high availability.