mongodb-memory-server/docs/api/interfaces/mongo-memory-instance-opts.md

---
id: mongo-memory-instance-opts
title: 'MongoMemoryInstanceOpts'
---

API Documentation of `MongoMemoryInstanceOpts`-Interface

## Values for `MongoMemoryInstanceOpts`

Inherits from [`MongoMemoryInstanceOptsBase`](#values-for-mongomemoryinstanceoptsbase).

### auth

Typings: `auth?: boolean`  
Default: `false`

Set which option auth argument to add:

- if `true`, add `--auth`
- if `false`, add `--noauth`

This options gets automatically set (overwritten) when using `createAuth`.

### dbName

Typings: `dbName?: string`

Previously set the `dbName` for the `getUri` calls, but currently unused.

### ip

Typings: `ip?: string`

Set the ip to bind to, if defined will add the argument `--bind_ip` with the input string.

### replSet

Typings: `replSet?: string`

Set the ReplSet name to use, if defined will add the argument `--replSet` with the input string.

### keyfileLocation

Typings: `keyfileLocation?: string`

Set a custom location for where the keyfile for authentication will be stored, if defined will add the argument `--keyfile` with the input string.  
Only has a effect when used in a [`MongoMemoryReplSet`](../classes/mongo-memory-replset.md) and `auth` is enabled.  
This option will get automatically set when not manually defined.

## Values for `MongoMemoryInstanceOptsBase`

### args

Typings: `args?: string[]`

Set extra Arguments to add to the started instance, will likely overwrite arguments set by other options, depending on how the binary parses arguments.

### port

Typings: `port?: number`

When set, adds the `--port` argument with the input.  
This options will get automatically set with a free port that is found.

### dbPath

Typings: `dbPath?: string`

When set, adds the `--dbpath` argument with the input.  
This option will automatically be set with a directory generated by [`mkdtemp`](https://nodejs.org/api/fs.html#fspromisesmkdtempprefix-options).

### storageEngine

Typings: `storageEngine?: StorageEngine`  
Default: `ephemeralForTest` (unless mongodb version is `7.0.0`, where its `wiredTiger`)

Set which storage engine to use, uses [`StorageEngine`](#helper-type-storageengine).

### replicaMemberConfig

Typings: `replicaMemberConfig?: ReplicaMemberConfig`

Set custom a custom Replica Member Config, uses [`ReplicaMemberConfig`](./mongo-memory-instance-replicamemberconfig.md).  
Only has a effect when started with [`MongoMemoryReplSet`](../classes/mongo-memory-replset.md).

## Helper Type `StorageEngine`

Typings: `StorageEngine = 'ephemeralForTest' | 'wiredTiger'`

Storage Engines supported by mongodb, see [MongoDB Storage Engines](https://www.mongodb.com/docs/manual/core/storage-engines/).

Custom Explanation:

- `ephemeralForTest` is a in-memory storage engine, which stores everything in RAM, which is great to use when wanting a simple database testing backend, is not the same as the Enterprise In-Memory Engine
- `wiredTiger` is a storage engine which stores data on disk.

:::warning
MongoDB has stated that storage-engine `ephemeralForTest` is unstable and has been deprecated, it will be removed with mongodb 7.

In MMS there has been no observation of `ephemeralForTest` being unstable (aside from some missing features) and will continue to be the default until mongodb-memory-server changes to a version where `ephemeralForTest` is not present anymore.

With mongodb-memory-server 9.0.0, if mongodb 7.0.0 or higher is used, `wiredTiger` is the default engine.
:::