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Fast in-process flat file database for Node.js that supports JSON and caches all data in memory. All data is persisted to an open file using a append-only algorithm ensuring compact file sizes and strong consistency.

npm install flat-file-db

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Pass a database file to use to the flat-file-db constructor and wait for the database to open. When it is open all data has been loaded into memory.

var flatfile = require('flat-file-db');
var db = flatfile('/tmp/my.db');
db.on('open', function() {
    db.put('hello', {world:1});  // store some data 
    console.log(db.get('hello')) // prints {world:1} 
    db.put('hey', {world:2}, function() {
        // 'hey' is now fully persisted 

If you don't want to wait for it to open use flatfile.sync

var db = flatfile.sync('/tmp/my.db');
console.log(db.get('hello')); // prints {world:1} 

If you issue multiple writes the last one will always win

for (var i = 0; i < 10; i++) {
    db.put('test', {count:i}, ...);
console.log(db.get('test')); // {count:9} which also the persisted value of 'test' 


  • db = flatfile(path, opts) Create a new db instance. Per default fsync is called on all puts. To disable this set opts.fsync = false

  • db = flatfile.sync(path, opts) Same as above except you do not need to wait for the open event

  • db.put(key, val, [cb]) Insert or update new key

  • db.del(key, [cb]) Delete a key

  • db.get(key) -> doc Get the value of a key

  • db.has(key) -> bool True if db has key

  • db.keys() -> list Get all keys as an array

  • db.clear([cb]) Clears the database of all values

  • db.close() Close the database


  • db.on('open') Fired when the db is open and ready for use.

  • db.on('close') Fired when the db is fully closed

  • db.on('drain') All puts and deletes are flushed to disk