MongoDB

{{See also|MongoDB Inc.#History}}

The American software company 10gen began developing MongoDB in 2007 as a component of a planned platform-as-a-service product. In 2009, the company shifted to an open-source development model and began offering commercial support and other services. In 2013, 10gen changed its name to MongoDB Inc.{{cite web |title=10gen embraces what it created, becomes MongoDB Inc. |url=http://gigaom.com/2013/08/27/10gen-embraces-what-it-created-becomes-mongodb-inc/ |url-status=live |archive-url=https://web.archive.org/web/20160305015624/https://gigaom.com/2013/08/27/10gen-embraces-what-it-created-becomes-mongodb-inc/ |archive-date=March 5, 2016 |access-date=January 29, 2016 |work=Gigaom |language=en-US}}

On October 20, 2017, MongoDB became a publicly traded company, listed on NASDAQ as MDB with an IPO price of $24 per share.{{cite web|last1=Witkowski|first1=Wallace|title=MongoDB shares rally 34% in first day of trading above elevated IPO price|url=https://www.marketwatch.com/story/mongodb-shares-rally-above-already-elevated-ipo-price-2017-10-19|website=MarketWatch|publisher=Dow Jones|access-date=February 26, 2018|date=October 21, 2017|archive-url=https://web.archive.org/web/20180226092020/https://www.marketwatch.com/story/mongodb-shares-rally-above-already-elevated-ipo-price-2017-10-19|archive-date=February 26, 2018|url-status=live}}

On November 8, 2018, with the stable release 4.0.4, the software's license changed from AGPL 3.0 to SSPL.{{cite web|url=https://www.mongodb.com/docs/manual/release-notes/4.0-changelog/#build-and-packaging-20|title=4.0 Changelog – 4.0.4 Changelog – Build and Packaging|access-date=2023-06-28}}{{cite web|url=https://www.mongodb.com/docs/manual/release-notes/4.0/#4.0.4---nov-8--2018|title=Release Notes for MongoDB 4.0 – 4.0.4 – Nov 8, 2018|access-date=2023-06-28}}

On October 30, 2019, MongoDB teamed with Alibaba Cloud to offer Alibaba Cloud customers a MongoDB-as-a-service solution. Customers can use the managed offering from Alibaba's global data centers.{{cite web |last=Betz |first=Brandy |date=October 30, 2019 |title=MongoDB teams with Alibaba Cloud |website=Seeking Alpha |url=https://seekingalpha.com/news/3511543-mongodb-teams-alibaba-cloud |access-date=2019-10-31}}

As of May 2025, MongoDB was the fifth most popular database software.{{cite web |last=Kanaracus |first=Chris |date=January 11, 2019 |title=AWS, MongoDB database collision stirs open source tensions |url=https://www.techtarget.com/searchaws/news/252455751/AWS-MongoDB-database-collision-stirs-open-source-tensions |access-date=August 10, 2024 |website=SearchAWS}}{{cite web |date=January 1, 2024 |title=DB-Engines Ranking |url=https://db-engines.com/en/ranking |access-date=August 27, 2024 |website=DB-Engines}} It focuses mostly on managing large databases of unstructured, "messy" data.{{cite web |last=Bort |first=Julie |date=October 20, 2017 |title=People told the MongoDB founders they were 'completely crazy' and now the company is worth $1.6 billion |url=https://www.businessinsider.com/people-told-the-mongodb-founders-they-were-completely-crazy-2017-10 |access-date=August 9, 2024 |website=Business Insider}}{{cite web |last=Joseph |first=Lison |date=December 3, 2013 |title=MongoDB startup hired by Aadhaar got funds from CIA VC arm |url=https://economictimes.indiatimes.com/news/politics-and-nation/mongodb-startup-hired-by-aadhaar-got-funds-from-cia-vc-arm/articleshow/26755706.cms?prtpage=1 |access-date=August 9, 2024 |website=The Economic Times}} It's typically used for mobile and web apps that commonly use unstructured databases.{{cite web |last=Sawers |first=Paul |date=April 28, 2024 |title=MongoDB CEO Dev Ittycheria talks AI hype and the database evolution as he crosses 10-year mark |url=https://techcrunch.com/2024/04/28/mongodb-ceo-dev-ittycheria-interview-ai-hype-database-evolution/ |access-date=August 11, 2024 |website=TechCrunch}} As of 2024, there were 50,000 MongoDB customers. MongoDB was originally best known as a NoSQL database product.{{cite web |last=Lardinois |first=Frederic |date=March 7, 2017 |title=MongoDB's Atlas database service goes freemium |url=https://techcrunch.com/2017/03/07/mongodbs-hosted-atlas-database-service-goes-freemium/ |access-date=August 10, 2024 |website=TechCrunch}} The company released a database as-a-service product called Atlas in 2016{{cite web |last=Sawers |first=Paul |date=October 10, 2018 |title=MongoDB to acquire cloud database provider MLab for $68 million |url=https://venturebeat.com/business/mongodb-to-acquire-cloud-database-provider-mlab-for-68-million/ |access-date=August 10, 2024 |website=VentureBeat}} that became 70 percent of MongoDB's revenue by 2024. Over time, MongoDB added analytics, transactional databases,{{cite web |last=Baer |first=Tony |date=June 21, 2022 |title=Are Snowflake and MongoDB on a collision course? |url=https://venturebeat.com/data-infrastructure/are-snowflake-and-mongodb-on-a-collision-course/ |access-date=August 11, 2024 |website=VentureBeat}} encryption,{{cite web |last2=Newman |first2=Lily Hay |date=June 7, 2022 |title=A Long-Awaited Defense Against Data Leaks May Have Just Arrived |url=https://www.wired.com/story/mongodb-queryable-encryption-databases/ |access-date=August 11, 2024 |website=WIRED}} vector databases, ACID, migration features, and other enterprise tools.{{cite web |last=Brust |first=Andrew |date=June 7, 2022 |title=MongoDB fires up new cloud, on-premises releases |url=https://venturebeat.com/data-infrastructure/mongodb-fires-up-new-cloud-on-premise-releases/ |access-date=August 11, 2024 |website=VentureBeat}} Initially, the MongoDB software was free and open source under the AGPL license. MongoDB adopted an SSPL (server side public license) for future releases starting in 2018.{{cite web |last=Lardinois |first=Frederic |date=October 16, 2018 |title=MongoDB switches up its open-source license |url=https://techcrunch.com/2018/10/16/mongodb-switches-up-its-open-source-license/ |access-date=August 10, 2024 |website=TechCrunch}}

MongoDB supports field, range query and regular-expression searches.{{cite web |url=https://dzone.com/articles/why-mongodb-is-worth-choosing-find-reasons |title=Why MongoDB is the way to go |publisher=DZone |author=Davis Kerby |access-date=July 6, 2017 |archive-url=https://web.archive.org/web/20180612141153/https://dzone.com/articles/why-mongodb-is-worth-choosing-find-reasons |archive-date=June 12, 2018 |url-status=live }} Queries can return specific fields of documents and also include user-defined JavaScript functions. Queries can also be configured to return a random sample of results of a given size.

Fields in a MongoDB document can be indexed with primary and secondary indices.

MongoDB provides high availability with replica sets.{{cite web|url=http://clusterhq.com/2016/03/14/ridiculously-fast-mongodb-replica-recovery-with-flocker/|title=Ridiculously fast MongoDB replica recovery Part 1 of 2|publisher=ClusterHQ|archive-url=https://web.archive.org/web/20171030014315/http://clusterhq.com/2016/03/14/ridiculously-fast-mongodb-replica-recovery-with-flocker/|archive-date=October 30, 2017|url-status=usurped}} A replica set consists of two or more copies of the data. Each replica-set member may act in the role of primary or secondary replica at any time. All writes and reads are done on the primary replica by default. Secondary replicas maintain a copy of the data of the primary using built-in replication. When a primary replica fails, the replica set automatically conducts an election process to determine which secondary should become the primary. Secondaries can optionally serve read operations, but that data is only eventually consistent by default.

If the replicated MongoDB deployment only has a single secondary member, a separate daemon called an arbiter must be added to the set. It has the single responsibility of resolving the election of the new primary.{{cite web|url=https://docs.mongodb.com/manual/core/replica-set-arbiter/|title=MongoDB docs – Replica Set Arbiter|access-date=2021-04-09}} As a consequence, an ideal distributed MongoDB deployment requires at least three separate servers, even in the case of just one primary and one secondary.

MongoDB scales horizontally using sharding.{{Cite web|url=https://severalnines.com/blog/turning-mongodb-replica-set-sharded-cluster|title=Turning MongoDB Replica Set to a Sharded Cluster|website=Severalnines|date=May 11, 2013 |archive-url=https://web.archive.org/web/20161125114334/http://severalnines.com/blog/turning-mongodb-replica-set-sharded-cluster|archive-date=November 25, 2016|url-status=live}} The user chooses a shard key, which determines how the data in a collection will be distributed. The data is split into ranges (based on the shard key) and distributed across multiple shards, which are masters with one or more replicas. Alternatively, the shard key can be hashed to map to a shard – enabling an even data distribution.

MongoDB can run over multiple servers, balancing the load or duplicating data to keep the system functional in case of hardware failure.

MongoDB can be used as a file system, called GridFS, with load-balancing and data-replication features over multiple machines for storing files.

This function, called a grid file system,{{cite web|url=https://www.compose.com/articles/gridfs-and-mongodb-pros-and-cons/|title=GridFS & MongoDB: Pros & Cons|website=Compose|date=June 5, 2014 |archive-url=https://web.archive.org/web/20170910172626/https://www.compose.com/articles/gridfs-and-mongodb-pros-and-cons/|archive-date=September 10, 2017|url-status=live}} is included with MongoDB drivers. MongoDB exposes functions for file manipulation and content to developers. GridFS can be accessed using the mongofiles utility or plugins for Nginx{{cite web |url=https://github.com/mdirolf/nginx-gridfs |title=NGINX plugin for MongoDB source code |website=GitHub |access-date=September 10, 2016 |archive-url=https://web.archive.org/web/20160411101948/https://github.com/mdirolf/nginx-gridfs |archive-date=April 11, 2016 |url-status=live }} and lighttpd.{{cite web |url=http://bitbucket.org/bwmcadams/lighttpd-gridfs/src/ |title=lighttpd plugin for MongoDB source code |website=Bitbucket |access-date=June 28, 2010 |archive-url=https://web.archive.org/web/20110807205643/https://bitbucket.org/bwmcadams/lighttpd-gridfs/src/ |archive-date=August 7, 2011 |url-status=live }} GridFS divides a file into parts, or chunks, and stores each of those chunks as a separate document.{{cite web |url=http://www.expertstown.com/mongodb-overview/ |title=MongoDB overview |work=Expertstown |author=Malick Md |access-date=February 27, 2014 |archive-url=https://web.archive.org/web/20140305160652/http://www.expertstown.com/mongodb-overview/ |archive-date=March 5, 2014 |url-status=usurped }}

MongoDB provides three ways to perform aggregation: the aggregation pipeline, the map-reduce function and single-purpose aggregation methods.{{Cite web|url=https://docs.mongodb.com/manual/aggregation/|title=Aggregation — MongoDB Manual|website=docs.mongodb.com|language=en|access-date=August 14, 2018|archive-url=https://web.archive.org/web/20181129141455/https://docs.mongodb.com/manual/aggregation/|archive-date=November 29, 2018|url-status=live}}

Map-reduce can be used for batch processing of data and aggregation operations. However, according to MongoDB's documentation, the aggregation pipeline provides better performance for most aggregation operations.{{Cite web|url=https://docs.mongodb.com/manual/core/map-reduce/|title=Map-Reduce — MongoDB Manual|website=docs.mongodb.com|language=en|access-date=August 14, 2018|archive-url=https://web.archive.org/web/20180814232606/https://docs.mongodb.com/manual/core/map-reduce/|archive-date=August 14, 2018|url-status=live}}

The aggregation framework enables users to obtain results similar to those returned by queries that include the SQL GROUP BY clause. Aggregation operators can be strung together to form a pipeline, analogous to Unix pipes. The aggregation framework includes the $lookup operator, which can join documents from multiple collections, as well as statistical operators such as standard deviation.

JavaScript can be used in queries, aggregation functions (such as MapReduce) and sent directly to the database to be executed.

MongoDB supports fixed-size collections called capped collections. This type of collection maintains insertion order and, once the specified size has been reached, behaves like a circular queue.

MongoDB supports multi-document ACID transactions since the 4.0 release in June 2018.{{Cite web|url=https://wikibon.com/mongodb-drives-nosql-deeply-enterprise-opportunities/|title=MongoDB Drives NoSQL More Deeply into Enterprise Opportunities|date=June 27, 2018|access-date=August 7, 2018|archive-url=https://web.archive.org/web/20180807125210/https://wikibon.com/mongodb-drives-nosql-deeply-enterprise-opportunities/|archive-date=August 7, 2018|url-status=live}}

The MongoDB Community Edition is free and available for Windows, Linux and macOS.{{Cite news|url=https://www.mongodb.com/download-center#community|title=MongoDB Download Center|work=MongoDB|access-date=August 14, 2018|language=en-us|archive-url=https://web.archive.org/web/20180814232604/https://www.mongodb.com/download-center#community|archive-date=August 14, 2018|url-status=live}}

MongoDB Enterprise Server is the commercial edition of MongoDB and is available as part of the MongoDB Enterprise Advanced subscription.{{Cite news|url=https://www.mongodb.com/download-center#enterprise|title=MongoDB Download Center|work=MongoDB|access-date=August 14, 2018|language=en-us|archive-url=https://web.archive.org/web/20180814232604/https://www.mongodb.com/download-center#enterprise|archive-date=August 14, 2018|url-status=live}}

MongoDB is also available as an on-demand, fully managed service. MongoDB Atlas runs on AWS, Microsoft Azure and Google Cloud Platform.{{Cite news|url=https://techcrunch.com/2018/06/27/mongodb-launches-global-clusters-to-put-geographic-data-control-within-reach-of-anyone/|title=MongoDB launches Global Clusters to put geographic data control within reach of anyone|work=MongoDB|access-date=June 27, 2018|language=en-us|archive-url=https://web.archive.org/web/20180627191051/https://techcrunch.com/2018/06/27/mongodb-launches-global-clusters-to-put-geographic-data-control-within-reach-of-anyone/|archive-date=June 27, 2018|url-status=live}}

On March 10, 2022, MongoDB warned its users in Russia and Belarus that their data stored on the MongoDB Atlas platform will be destroyed as a result of American sanctions related to the Russo-Ukrainian War.{{Cite web|url=https://www.securitylab.ru/news/530550.php/|title=MongoDB уничтожит все данные Россиян и Белорусов|first=Alexander|last=Antipov|date=March 11, 2022|website=www.securitylab.ru}}

MongoDB has official drivers for major programming languages and development environments.{{cite web |url=https://github.com/mongodb/mongo |title=GitHub – mongodb/mongo |author=MongoDB |publisher=GitHub |access-date=July 6, 2017 |archive-url=https://web.archive.org/web/20170729033153/https://github.com/mongodb/mongo |archive-date=July 29, 2017 |url-status=live }} There are also a large number of unofficial or community-supported drivers for other programming languages and frameworks.

File:Robomongo 0.8.5 - insertion.png

The primary interface to the database has been the mongo shell. Since MongoDB 3.2, MongoDB Compass is introduced as the native GUI. There are products and third-party projects that offer user interfaces for administration and data viewing.{{cite web|last1=Ma|first1=Jason|title=Visualizing Your Data With MongoDB Compass|url=https://dzone.com/articles/visualizing-your-data-with-mongodb-compass|website=Dzone|publisher=Dzone.com|access-date=July 6, 2017|archive-url=https://web.archive.org/web/20180522041739/https://dzone.com/articles/visualizing-your-data-with-mongodb-compass|archive-date=May 22, 2018|url-status=live}}

As of October 2018, MongoDB is released under the Server Side Public License (SSPL), a non-free license developed by the project. It replaces the GNU Affero General Public License, and is nearly identical to the GNU General Public License version 3, but requires that those making the software publicly available as part of a "service" must make the service's entire source code (insofar that a user would be able to recreate the service themselves) available under this license. By contrast, the AGPL only requires the source code of the licensed software to be provided to users when the software is conveyed over a network.{{Cite news|url=https://www.zdnet.com/article/its-mongodbs-turn-to-change-its-open-source-license/|title=It's MongoDB's turn to change its open source license|last=Baer|first=Tony|work=ZDNet|access-date=October 16, 2018|language=en|archive-url=https://web.archive.org/web/20181031132035/https://www.zdnet.com/article/its-mongodbs-turn-to-change-its-open-source-license/|archive-date=October 31, 2018|url-status=live}}{{Cite news|url=https://techcrunch.com/2018/10/16/mongodb-switches-up-its-open-source-license/|title=MongoDB switches up its open source license|work=TechCrunch|access-date=October 16, 2018|language=en-US|archive-url=https://web.archive.org/web/20181016141702/https://techcrunch.com/2018/10/16/mongodb-switches-up-its-open-source-license/|archive-date=October 16, 2018|url-status=live}} The SSPL was submitted for certification to the Open Source Initiative but later withdrawn.{{Cite web|url=https://arstechnica.com/information-technology/2019/10/is-the-software-world-taking-too-much-from-the-open-source-community/|title=In 2019, multiple open source companies changed course—is it the right move?|first=Ars|last=Staff|date=October 16, 2019|website=Ars Technica}} In January 2021, the Open Source Initiative stated that SSPL is not an open source license.{{Cite web|url=https://opensource.org/node/1099|title=The SSPL is Not an Open Source License|last=OSI|date=January 19, 2021|website=OSI|access-date=August 20, 2022|archive-date=August 20, 2022|archive-url=https://web.archive.org/web/20220820133332/https://opensource.org/node/1099/|url-status=dead}} The language drivers are available under an Apache License. In addition, MongoDB Inc. offers proprietary licenses for MongoDB. The last versions licensed as AGPL version 3 are 4.0.3 (stable) and 4.1.4.{{Cite web |title=GitHub – mongodb/mongo at r4.0.3 |url=https://github.com/mongodb/mongo/tree/r4.0.3 |access-date=2024-01-18 |website=GitHub |language=en}}

MongoDB has been removed from the Debian, Fedora and Red Hat Enterprise Linux distributions because of the licensing change. Fedora determined that the SSPL version 1 is not a free software license because it is "intentionally crafted to be aggressively discriminatory" towards commercial users.{{Cite web|url=https://www.zdnet.com/article/mongodb-open-source-server-side-public-license-rejected/|title=MongoDB "open-source" Server Side Public License rejected|last=Vaughan-Nichols|first=Steven J.|website=ZDNet|language=en|access-date=January 17, 2019|archive-url=https://web.archive.org/web/20190116202120/https://www.zdnet.com/article/mongodb-open-source-server-side-public-license-rejected/|archive-date=January 16, 2019|url-status=live}}{{Cite web|url=https://www.geekwire.com/2019/mongodbs-licensing-changes-led-red-hat-drop-database-latest-version-server-os/|title=MongoDB's licensing changes led Red Hat to drop the database from the latest version of its server OS|date=January 16, 2019|website=GeekWire|language=en-US|access-date=January 17, 2019|archive-url=https://web.archive.org/web/20190117035708/https://www.geekwire.com/2019/mongodbs-licensing-changes-led-red-hat-drop-database-latest-version-server-os/|archive-date=January 17, 2019|url-status=live}}

Because of MongoDB's default security configuration, which allows any user full access to the database, data from tens of thousands of MongoDB installations has been stolen. Furthermore, many MongoDB servers have been held for ransom.{{cite web|last1=Krebs|first1=Brian|title=Extortionists Wipe Thousands of Databases, Victims Who Pay Up Get Stiffed|url=https://krebsonsecurity.com/2017/01/extortionists-wipe-thousands-of-databases-victims-who-pay-up-get-stiffed/|website=krebsonsecurity.com|publisher=Brian Krebs|access-date=January 11, 2017|archive-url=https://web.archive.org/web/20170111021626/http://krebsonsecurity.com/2017/01/extortionists-wipe-thousands-of-databases-victims-who-pay-up-get-stiffed/|archive-date=January 11, 2017|url-status=live}}{{cite web|last1=Constantin|first1=Lucian|title=Ransomware groups have deleted over 10,000 MongoDB databases|url=http://www.computerworld.com/article/3155260/security/ransomware-groups-have-deleted-over-10000-mongodb-databases.html|website=Computer World|date=January 6, 2017 |publisher=IDG|access-date=January 11, 2017|archive-url=https://web.archive.org/web/20170110141219/http://computerworld.com/article/3155260/security/ransomware-groups-have-deleted-over-10000-mongodb-databases.html|archive-date=January 10, 2017|url-status=live}} In September 2017, Davi Ottenheimer head of product security at MongoDB, proclaimed that measures had been taken to defend against these risks.{{cite web |last1=Ottenheimer |first1=Davi |title=How to Avoid a Malicious Attack That Ransoms Your Data |url=https://www.mongodb.com/blog/post/update-how-to-avoid-a-malicious-attack-that-ransoms-your-data |website=www.mongodb.com |access-date=June 22, 2021}}

From the MongoDB 2.6 release onward, the binaries for the official MongoDB RPM and DEB packages bind to localhost by default. From MongoDB 3.6, this default behavior was extended to all MongoDB packages across all platforms. As a result, all networked connections to the database are denied unless explicitly configured by an administrator.{{cite web|title=MongoDB Bind IP Compatibility|url=https://docs.mongodb.com/master/release-notes/3.6-compatibility/#bind-ip-compatibility|website=MongoDB|publisher=MongoDB|access-date=March 5, 2019|archive-url=https://web.archive.org/web/20190306043704/https://docs.mongodb.com/master/release-notes/3.6-compatibility/#bind-ip-compatibility|archive-date=March 6, 2019|url-status=live}}

In some failure scenarios in which an application can access two distinct MongoDB processes that cannot access each other, it is possible for MongoDB to return stale reads. It is also possible for MongoDB to roll back writes that have been acknowledged.{{cite web|url=https://aphyr.com/posts/322-call-me-maybe-mongodb-stale-reads|author=Kyle Kingsbury|title=Call me maybe: MongoDB stale reads|date=April 20, 2015|access-date=July 4, 2015|archive-url=https://web.archive.org/web/20150815170715/https://aphyr.com/posts/322-call-me-maybe-mongodb-stale-reads|archive-date=August 15, 2015|url-status=live}} The issue was addressed in version 3.4.0, released in November 2016,{{Cite web|url=https://docs.mongodb.com/manual/release-notes/3.4|title=Release Notes for MongoDB 3.4|website=MongoDB Manual|access-date=April 6, 2018|archive-url=https://web.archive.org/web/20180814175445/https://docs.mongodb.com/manual/release-notes/3.4/|archive-date=August 14, 2018|url-status=live}} and applied to earlier releases from v3.2.12 onward.{{Cite web|url=https://jepsen.io/analyses/mongodb-3-4-0-rc3|title=MongoDB 3.4.0-rc3|last=Kingsbury|first=Kyle|date=February 7, 2017|website=Jepsen|archive-url=https://web.archive.org/web/20171023001543/http://jepsen.io/analyses/mongodb-3-4-0-rc3|archive-date=October 23, 2017|url-status=live}}

Before version 2.2, locks were implemented on a per-server-process basis. With version 2.2, locks were implemented at the database level.{{cite web |url=https://scalegrid.io/blog/atomicity-isolation-concurrency-in-mongodb |title=Atomicity, isolation & concurrency in MongoDB |website=scalegrid.io |access-date=June 28, 2017 |archive-url=https://web.archive.org/web/20170910125308/https://scalegrid.io/blog/atomicity-isolation-concurrency-in-mongodb/ |archive-date=September 10, 2017 |url-status=live }} Beginning with version 3.0,{{cite web |url=https://www.datanami.com/2015/02/03/mongodb-goes-pluggable-storage-engines |title=MongoDB Goes Pluggable with Storage Engines |date=March 5, 2015 |publisher=datanami.com |access-date=June 28, 2017 |archive-url=https://web.archive.org/web/20170704035137/https://www.datanami.com/2015/02/03/mongodb-goes-pluggable-storage-engines/ |archive-date=July 4, 2017 |url-status=live }} pluggable storage engines are available, and each storage engine may implement locks differently. With MongoDB 3.0, locks are implemented at the collection level for the MMAPv1 storage engine,{{cite web |url=http://www.arborian.com/2016/03/11/mongodb-mmapv1-wiredtiger-and-queues |title=MongoDB, MMAPv1, WiredTiger, Locking, and Queues |author=Arborian Consulting |publisher=Arborian Consulting |access-date=June 28, 2017 |archive-url=https://web.archive.org/web/20170619140103/http://www.arborian.com/2016/03/11/mongodb-mmapv1-wiredtiger-and-queues/ |archive-date=June 19, 2017 |url-status=live }} while the WiredTiger storage engine uses an optimistic concurrency protocol that effectively provides document-level locking.{{cite web |url=http://objectrocket.com/blog/company/mongodb-wiredtiger |title=MongoDB 3.0 WiredTiger Compression and Performance |author=Kenny Gorman |date=October 2015 |publisher=Objectrocket.com/ |access-date=June 28, 2017 |archive-url=https://web.archive.org/web/20170616134542/http://objectrocket.com/blog/company/mongodb-wiredtiger |archive-date=June 16, 2017 |url-status=live }} Even with versions prior to 3.0, one approach to increase concurrency is to use sharding.{{cite web |url=http://www.mikitamanko.com/blog/2013/12/06/mongodb-performance-bottlenecks-optimization-strategies-for-mongodb/ |title=MongoDB performance bottlenecks, optimization Strategies for MongoDB |author=Mikita Manko |publisher=mikitamanko.com |access-date=July 5, 2017 |archive-url=https://web.archive.org/web/20170719095251/http://www.mikitamanko.com/blog/2013/12/06/mongodb-performance-bottlenecks-optimization-strategies-for-mongodb/ |archive-date=July 19, 2017 |url-status=usurped }} In some situations, reads and writes will yield their locks. If MongoDB predicts that a page is unlikely to be in memory, operations will yield their lock while the pages load. The use of lock yielding expanded greatly in version 2.2.{{cite web |url=https://scalegrid.io/blog/atomicity-isolation-concurrency-in-mongodb/ |title=Atomicity, isolation & concurrency in MongoDB |author=scalegrid.io |date=September 12, 2013 |publisher=scalegrid.io |access-date=July 5, 2017 |archive-url=https://web.archive.org/web/20170910125308/https://scalegrid.io/blog/atomicity-isolation-concurrency-in-mongodb/ |archive-date=September 10, 2017 |url-status=live }}

Until version 3.3.11, MongoDB could not perform collation-based sorting and was limited to bytewise comparison via memcmp, which would not provide correct ordering for many non-English languages when used with a Unicode encoding. The issue was fixed on August 23, 2016.

Prior to MongoDB 4.0, queries against an index were not atomic. Documents that were updated while queries was running could be missed.{{Cite web|url=https://blog.meteor.com/mongodb-queries-dont-always-return-all-matching-documents-654b6594a827|title=MongoDB queries don't always return all matching documents!|first=David|last=Glasser|date=June 7, 2016|website=Meteor Blog}} The introduction of the snapshot read concern in MongoDB 4.0 eliminated this risk.{{cite web|title=MongoDB Docs|url=https://docs.mongodb.com/master/reference/read-concern-snapshot/|access-date=March 5, 2019|archive-url=https://web.archive.org/web/20190306043303/https://docs.mongodb.com/master/reference/read-concern-snapshot/|archive-date=March 6, 2019|url-status=live}}

MongoDB claimed that version 3.6.4 had passed "the industry's toughest data safety, correctness, and consistency tests" by Jepsen, and that "MongoDB offers among the strongest data consistency, correctness, and safety guarantees of any database available today."{{cite web |title=MongoDB and Jepsen |url=https://www.mongodb.com/jepsen |url-status=dead |archive-url=https://web.archive.org/web/20200508173236/https://www.mongodb.com/jepsen |archive-date=May 8, 2020 |access-date=August 4, 2023 |website=MongoDB}} Jepsen, which describes itself as a "distributed systems safety research company," disputed both claims on Twitter, saying, "In that report, MongoDB lost data and violated causal by default." In its May 2020 report on MongoDB version 4.2.6, Jepsen wrote that MongoDB had only mentioned tests that version 3.6.4 had passed, and that version had 4.2.6 introduced more problems.{{cite web | last=Allen | first=Jonathan | title=Jepsen Disputes MongoDB's Data Consistency Claims | website=InfoQ | date=May 22, 2020 | url=https://www.infoq.com/news/2020/05/Jepsen-MongoDB-4-2-6/ | archive-url=https://web.archive.org/web/20230606073352/https://www.infoq.com/news/2020/05/Jepsen-MongoDB-4-2-6/ | archive-date=June 6, 2023 | url-status=live | access-date=August 4, 2023}} Jepsen's test summary reads in part:

Jepsen evaluated MongoDB version 4.2.6, and found that even at the strongest levels of read and write concern, it failed to preserve snapshot isolation. Instead, Jepsen observed read skew, cyclic information flow, duplicate writes, and internal consistency violations. Weak defaults meant that transactions could lose writes and allow dirty reads, even downgrading requested safety levels at the database and collection level. Moreover, the snapshot read concern did not guarantee snapshot unless paired with write concern majority—even for read-only transactions. These design choices complicate the safe use of MongoDB transactions.{{cite web | last=Kingsbury | first=Kyle | title=Jepsen: MongoDB 4.2.6 | website=Jepsen | date=May 15, 2020 | url=https://jepsen.io/analyses/mongodb-4.2.6 | archive-url=https://web.archive.org/web/20230529193121/https://jepsen.io/analyses/mongodb-4.2.6 | archive-date=May 29, 2023 | url-status=live | access-date=August 4, 2023}}

On May 26, Jepsen updated the report to say: "MongoDB identified a bug in the transaction retry mechanism which they believe was responsible for the anomalies observed in this report; a patch is scheduled for 4.2.8." The issue has been patched as of that version, and "Jepsen criticisms of the default write concerns have also been addressed, with the default write concern now elevated to the majority concern (w:majority) from MongoDB 5.0."{{cite web | title=MongoDB And Jepsen | website=MongoDB | url=https://www.mongodb.com/jepsen | archive-url=https://web.archive.org/web/20230610045930/https://www.mongodb.com/jepsen | archive-date=June 10, 2023 | url-status=live | access-date=August 4, 2023}}

MongoDB Inc. hosts an annual developer conference that has been called MongoDB World or MongoDB.live.{{Cite web|url=https://www.mongodb.com/world|title=MongoDB World|website=www.mongodb.com|access-date=April 10, 2019|archive-url=https://web.archive.org/web/20190426073512/https://www.mongodb.com/world|archive-date=April 26, 2019|url-status=live}}

{{Portal|Free and open-source software}}

• Couchbase
• Apache Cassandra
• BSON, the binary JSON format that MongoDB uses for data storage and transfer
• List of server-side JavaScript implementations
• MEAN, a solutions stack using MongoDB as the database
• Server-side scripting
• Amazon DocumentDB, a proprietary database service designed for MongoDB compatibility
• Azure Cosmos DB, a proprietary database service suite designed for multi-database compatibility including MongoDB

{{Reflist|30em}}

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{{Refend}}

{{Commons category}}

• {{Official website}}

{{NodeJs}}

{{Authority control}}

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