MongoDB vs Redis
MongoDB stores JSON documents and is sold mainly as the Atlas cloud service. Redis keeps data in memory for sub-millisecond reads and is usually run beside a primary database for caches and sessions. Both ladders start free but cap hard: 512 MB on Atlas Free against 30 MB on Redis Free, and Redis Pro carries a monthly minimum.
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Choose MongoDB ifyou need a primary store for document data and want to climb from a free cluster to dedicated hardware.
Choose Redis ifyou need fast reads for caching, sessions or search beside a main database and can budget for memory as the main cost driver.
MongoDB and Redis side by side
| MongoDB | Redis | |
|---|---|---|
| Our database management system rank | #5 of 19 | #6 of 19 |
| Established in | United States | United States |
| List price, 2 November 2026 | Hourly billing. Dedicated starts at $56.94 per month and spans 10 GB to 4 TB; Flex tops out at $30 per month for 5 GB; Free is 512 MB (Atlas) | Free (30 MB); Essentials from an hourly rate, $5 per month total, 250 MB to 100 GB; Pro from an hourly rate, minimum $200 per month |
| Free tier | Yes | Yes |
| Open source | — | — |
| Self-hostable | — | — |
| Built for | Teams building around JSON documents who prefer a managed cloud service | Teams already running Redis who want vector queries beside their cache |
| Not for | Buyers who need an OSI-approved licence for the server | Buyers who need cheap storage for very large vector collections |
Both are reviewed in full in our database management system ranking: MongoDB and Redis.
Where they differ
MongoDB 2 · Redis 2 · open 1- 01
Free allowance
MongoDB Atlas Free holds 512 MB of storage. Redis Free is a single 30 MB database on a shared deployment with community support. For a prototype that holds real documents, the MongoDB free tier is the roomier one.
Edge: MongoDB
- 02
First paid step
Redis Essentials has a total of $5 per month for 250 MB to 100 GB, shared deployment. On MongoDB, 5 GB of Flex costs at most $30 per month, and Dedicated begins at $56.94 per month. If you only need a small paid cache, Redis is the cheaper entry.
Edge: Redis
- 03
Dedicated and production tiers
Redis Pro is a dedicated deployment with a minimum of $200 per month, with active-active, auto-tiering and up to 99.999% uptime. MongoDB Dedicated is billed hourly, from $56.94 per month, across 10 GB to 4 TB. MongoDB's published floor for dedicated hardware is much lower.
Edge: MongoDB
- 04
Licensing
From Redis 8 the code is offered under RSALv2, SSPLv1 or AGPLv3 at your choice, and only AGPLv3 is OSI approved. For MongoDB the server licence is the SSPL and nothing else. Redis gives you one OSI-approved option; MongoDB's own page names no such option for the server.
Edge: Redis
- 05
Role in the stack
Redis lists caching, session management, streaming and search with sub-millisecond reads, and its Flex option holds data at 10% RAM to cut cost. MongoDB sells Search, Vector Search and Stream Processing as separate priced Atlas services. They solve different problems, so neither wins this one.
Depends on the buyer
When neither fits
If you need a relational engine, or a masterless store for heavy write loads, look at PostgreSQL or Apache Cassandra.
MongoDB or Redis: questions
3 answersCan Redis replace MongoDB?
Redis is described by its own site around caching, sessions, streaming and search with data held in memory. MongoDB is a document database. Memory is the main price driver for Redis, so large datasets are costly there.
How big are the free plans?
MongoDB Atlas Free is 512 MB. Redis Free is 30 MB on a shared deployment with community support.
Is Redis still open source?
From Redis 8 you choose RSALv2, SSPLv1 or AGPLv3. Redis states RSALv2 and SSPLv1 are not open source licences, while AGPLv3 is OSI approved. Redis 7.2 and earlier stay BSD 3-clause.
Sources
Checked 2 November 2026- MongoDB pricing page: Atlas tiers; Search and Stream Processing priced apart.
- MongoDB Server Side Public License: SSPL for the server.
- Redis pricing page: Free 30 MB, Essentials $5 per month total, Pro minimum $200 per month, Flex at 10% RAM, workloads and sub-millisecond reads.
- Redis licences: RSALv2, SSPLv1 or AGPLv3 from Redis 8, only AGPLv3 OSI approved.
- Redis LICENSE.txt: Redis 7.2 and earlier remain BSD 3-clause.