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MongoDB vs Valkey

MongoDB logo

MongoDB

Technology

The developer data platform

From
Free
Rated
-
Full reviewWebsite
Valkey logo

Valkey

Databases

Open-source in-memory data store forked from Redis

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: MongoDB 16 MB maximum document size limits large single objects; Valkey younger project, so its track record is short even though the codebase is not
  • They diverge on capability: MongoDB covers Document model, Valkey covers Redis-compatible.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which MongoDB and Valkey actually diverge.

Attributes where MongoDB and Valkey differ
AttributeMongoDBValkey
Pricing modelUnknownOpen source, no licence fee; managed cloud billed separately
PlatformsCloud (Atlas), Self-hosted, Multi-cloud (AWS, Google Cloud, Azure)Linux, macOS, Docker, Self-hosted
CategoryTechnologyDatabases
Founded2007Unknown

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 MongoDB

  • Document model
  • Distributed architecture
  • ACID transactions
  • Real-time analytics
  • Full-text search
  • Time series data
  • Geospatial queries
  • Aggregation framework

Only in Valkey

  • Redis-compatible
  • BSD licensed
  • Rich data structures
  • Replication and persistence

What people use each for

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

MongoDB

  • Mobile applicationsnot Valkey
  • Content managementnot Valkey
  • Real-time analyticsnot Valkey
  • IoT applicationsnot Valkey
  • Gaming backendsnot Valkey

Valkey

  • Continuing on a permissively licensed in-memory store after the Redis licence changenot MongoDB
  • Caching and session storage where a foundation-governed project is a procurement requirementnot MongoDB
  • Migrating from Redis without rewriting application codenot MongoDB

Where each one falls short

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

MongoDB

  • 16 MB maximum document size limits large single objects
  • No native JOIN support for relational data operations
  • Higher memory usage due to storing field names with each document
  • Eventual consistency in distributed deployments can cause data stale reads

Valkey

  • Younger project, so its track record is short even though the codebase is not
  • Divergence from Redis grows over time, so compatibility is strongest near the fork point and weakens as both evolve
  • Ecosystem tooling and documentation still frequently assume Redis, leaving translation work

Pricing, plan by plan

MongoDB

Free
  • M0Free
    • 512 MB storage
    • Learning and exploration
  • M2$9/month
    • 2 GB storage
    • Development and testing
  • M5$25/month
    • 5 GB storage
  • M10+$56.94/month
    • Dedicated clusters for production

Valkey

Free
  • ValkeyFree
    • Full functionality
    • Self-hosted
    • No usage limits

Which should you pick?

Choose MongoDB if

  • You need document model.
  • You want to start without paying.
  • You work on Cloud (Atlas), Self-hosted, Multi-cloud (AWS, Google Cloud, Azure).
  • You also want distributed architecture.
MongoDB review

Choose Valkey if

  • You need redis-compatible.
  • You want to start without paying.
  • You work on Linux, macOS, Docker, Self-hosted.
  • You also want bsd licensed.
Valkey review

Questions people ask

Is MongoDB or Valkey better?
Neither clearly leads. MongoDB starts at Free and Valkey at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, MongoDB or Valkey?
MongoDB starts at Free and Valkey at Free.
Does MongoDB or Valkey run on more platforms?
MongoDB runs on Cloud (Atlas), Self-hosted, Multi-cloud (AWS, Google Cloud, Azure). Valkey runs on Linux, macOS, Docker, Self-hosted.
Can I use MongoDB for free?
Both have a free tier, so you can try either at no cost before committing.
What is MongoDB best used for?
MongoDB is most often used for mobile applications, content management, real-time analytics, iot applications. Of those, mobile applications and content management are not what Valkey is typically brought in for.
What can MongoDB do that Valkey cannot?
MongoDB covers Document model, Distributed architecture, ACID transactions, Real-time analytics. Valkey covers Redis-compatible, BSD licensed, Rich data structures, Replication and persistence.

Answered from the vendors’ own pages

MongoDB: Does MongoDB offer a free tier?

Yes. MongoDB Atlas offers an M0 free tier with 512 MB storage for learning and exploration, plus paid options starting at $9/month for M2 with 2 GB storage.

Source
Valkey: Is Valkey free?

Yes, BSD-licensed open source under the Linux Foundation.

MongoDB: Can I self-host MongoDB?

Yes. You can run MongoDB Community Edition on your own servers, or use MongoDB Enterprise Advanced for self-managed production deployments with enterprise features.

Source
Valkey: Why does Valkey exist?

Redis changed its licence away from BSD in 2024. Valkey is the community fork continuing under permissive terms, backed by AWS, Google Cloud and Oracle among others.

MongoDB: What is the maximum document size in MongoDB?

Documents are limited to 16 MB. For documents exceeding this limit, you can use MongoDB's GridFS API to store files larger than the maximum size.

Source
Valkey: Can I switch from Redis to Valkey?

At the fork point it is drop-in compatible with existing clients and data. The further both projects move from that point, the more you should verify the specific features you use.

MongoDB: Does MongoDB support ACID transactions?

Yes. MongoDB supports ACID transactions within a single document by default, and multi-document ACID transactions are available for replica sets and sharded clusters in MongoDB 4.0+.

Source
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