Abandoned Project

NeDB is a lightweight embedded document DBMS written in JavaScript. It supports Node.js, nw.js, Electron, and web browser environments. It is designed to be partially compatible with MongoDB's JSON-based query API. NeDB is useful for storing small amounts of data in memory. When the amount of data exceeds the bounds of what NeDB can hold effectively, switching to MongoDB is intended to be straightforward because it uses the same API.


In May 2013, Louis Chatriot began developing a lightweight embeddable and in memory database system that used a subset of the MongoDB API. It was completed in 2017 and now is on GitHub where individuals can contribute to the project by fixing several bugs but no additional features are being implemented currently. However, several separate teams have forked copies of the original NeDB database and began implementing their own ideas and additional features that weren't originally intended by the original creator.


Not Supported

Concurrency Control

Not Supported

NeDB is written completely in Javascript and since Javascript is inherently single-threaded, there is no concurrency in the system. Additionally, each process receives its own copy of the database, which means it can't sync the views that two different processes have of the data.

Data Model

Document / XML

NeDB is a document-based database system because it is built upon MongoDB.

Foreign Keys

Not Supported



NeDB supports indexing and helps provide a sufficient speed boost. It allows for indexing of any field, including those in nested documents. An index can be created at any point, even after data has been inserted. However, it is most efficient if done when the application is started because the index is created synchronously. The time to create an index is quite fast so it doesn't impact startup time too much. Additionally, indexes allow for the database to perform fast reads and writes.

Isolation Levels

Not Supported

NeDB does not support any isolation levels because no concurrency is guaranteed by the system.


Not Supported

Although MongoDB does support joins, NeDB does not because the only similarites between NeDB and MongoDB are the syntax for queries used in the API. Additionally, NeDB does not support joins because it is not a relational database but rather a document store database.


Not Supported

NeDB does not support logging because all data is stored in memory. However, a NeDB logger has been created that can be used to insert documents into a NeDB-readable database.

Query Interface

Custom API

The JavaScript API is a subset of MongoDB. The syntax for the query commands are the same as MongoDB, which allows for easy mitigation to MongoDB once the amount of data becomes too large for NeDB.

Storage Architecture


NeDB stores all databases in memory in order to perform fast find and query operations. Storing all the data in memory causes NeDB to only perform well on smaller datasets.

Storage Organization


NeDB uses an append-only format, which means all updates and deletes will be added to the end of the datafile. This is done for performance reasons. The database is automatically compacted whenever it is loaded within an application. It is possible to run manual compaction, but it requires everything else to be paused and can take some time to complete. Therefore, most applications don't need to do this.

Stored Procedures

Not Supported

System Architecture


NeDB uses an embedded database system approach. The database system is on the application when it is being run because it is imported to the application as a library. Additionally, the system is used through API calls, which are the same as MongoDB.

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