@erfanium/mylite

In-memory, in-process MySQL for Node.js. A drop-in for mysql2/promise backed by the Turso engine: no server to start, no socket, no container. Built for test suites.

const mysql = require('@erfanium/mylite'); // instead of 'mysql2/promise'

const pool = mysql.createPool({ database: 'app' });
await pool.query('create table users (id int auto_increment primary key, name varchar(255))');
const [result] = await pool.query('insert into users (name) values (?)', ['Ada']);
const [rows] = await pool.query('select * from users where id = ?', [result.insertId]);
await pool.end();

Or, in the spirit of PGlite, one isolated database per instance:

const { MyLite } = require('@erfanium/mylite');

const db = new MyLite();
await db.query('create table t (id int primary key)');
const pool = db.createPool(); // a regular mysql2 pool on this database
await db.close();             // frees the database

How it works

@erfanium/mylite exports everything mysql2/promise exports (it is also reachable as @erfanium/mylite/promise). The callback API of plain mysql2 is not wrapped. createPool, createConnection and createPoolCluster return real mysql2 objects whose transport is an in-memory stream to an engine running inside the process, so pooling, escaping, type casting and streaming are mysql2's own.

• database selects the in-memory database; it is created on first use. Connections that name the same database share it, different names are isolated. Host, port and credentials are ignored.
• A database lives until the process exits, dropDatabase(name) is called, or its MyLite instance is closed.
• An open connection keeps the process alive, like a socket. Set MYLITE_UNREF=1 to let the process exit with connections open.

To use it under an existing codebase without touching imports, alias the module in your test runner, for example in Vitest:

resolve: {
  alias: [
    { find: /^mysql2\/promise$/, replacement: '@erfanium/mylite' },
  ],
}

It is an emulation

Statements are translated to the engine's SQL, so this is not MySQL:

• Write transactions are serialized and FOR UPDATE is a plain read. Tests of lock contention prove nothing here.
• DECIMAL arithmetic is done in floating point and formatted to MySQL's scale.
• Rows a query does not order come back in primary key order, as InnoDB's clustered index would usually give; MySQL can differ when it picks a secondary index.
• A string literal shaped like an ISO datetime is normalized to MySQL's datetime form.
• Only the text protocol exists. execute() runs as query().
• Error codes match for duplicate keys, unknown tables and unknown columns; messages do not.

Keep a run against real MySQL as the reference.

Native binary

The engine ships as a prebuilt addon under prebuilds/<platform>-<arch>/. This build includes linux-x64 only. The source is the mysql/ directory of erfanium/turso; npm run build:native builds a binary for the current machine from that workspace, and MYLITE_NATIVE_PATH points the loader at a binary elsewhere.