Frequently Asked Questions (FAQ)

MongoDB Feature Support

Do you support MongoDB 4.0 or 4.2?

mLab does not support MongoDB version 4.0 or 4.2.

However, note that mLab has joined MongoDB, Inc. and is in the process of migrating databases to MongoDB Atlas. MongoDB Atlas does support versions 4.0 and above.

If you are interested in migrating now, please review the section of the above documentation about migrating now and open a support ticket at if you have any questions.

Which drivers and client libraries do you support?

We support all of the standard MongoDB drivers. We also have driver examples in many of the major languages including C#, Java, Node.js, PHP, Python, Ruby, etc..

Do you support features that aren’t in your management portal (e.g., Views)?

Yes. Our web-based management portal does not support every feature of MongoDB, but any database you create with mLab will support all the features supported by that MongoDB version.

For example, our management portal does not currently support Views. However, you can use the mongo shell or one of the standard MongoDB drivers to interface with Views.

Do your plans include oplog access (e.g., for oplog tailing)?

All of our for-pay plans include access to the local database which includes the oplog for your MongoDB deployment.

mLab’s Cloud-hosted MongoDB Offering

Will I be locked into your service?

You will not be locked into the mLab service. Here are some reasons why:

Which cloud providers and regions do you support?

We offer our MongoDB-hosting services on AWS, Google Cloud Platform, and Microsoft Azure in most of their regions worldwide.

What are the advantages of using mLab through one of our partners (e.g., Heroku)?

Many of our users provision mLab-hosted MongoDB deployments through one of our partners. There are two primary advantages to provisioning your deployment through a partner integration such as the Heroku Add-Ons marketplace: (1) The convenience of a single billing and vendor relationship; (2) The convenience of single-sign on between your application’s management portal and the mLab management portal.

In addition, some of our partner integrations automatically expose an environment variable to your application with your database deployment’s connection URI.

Note that some of the plans and features that we offer directly through are different from what’s available through our partners. As such, be sure to read the documentation published on the partner’s website (e.g., for Heroku,

In the event you decide to provision your mLab-hosted MongoDB deployments directly through instead of a partner, make sure that you provision your deployment in the same datacenter/region that your application is hosted in. For example, on Heroku, this would be either AWS US East or AWS EU West.

Do you charge extra for data transfer / network traffic?

No we do not. You will have to pay your hosting provider for network traffic in and out of your app’s instances, but the charges directly related to the instances hosting your mLab deployments are already included.

How do I choose the right plan for my needs?

Making sense of all the plan options in the context of your data-related requirements is not always an easy task. To aid you in this process, read the article where we discuss plan types and the factors to consider when choosing a plan.

Feel free to contact if you’d like our assistance in helping you figure out which plan will be best for you.

How do I upgrade/downgrade?

For subscriptions created directly in the mLab management portal (i.e., not as an add-on with one of our Platform-as-a-Service (PaaS) partners such as Heroku), you can change the plan for your MongoDB deployment by following the instructions documented in our article about database subscriptions.

For subscriptions created via add-ons with one of our partners, refer to the add-on documentation available on the partner’s site.

Which browsers do you support in the mLab management portal?

We only support the following desktop browsers when logged into mLab’s management portal:

Desktop browser Version
Chrome (recommended) 56 and up
Firefox 51 and up
Safari 9 and up
Edge 14 and up
Internet Explorer 11

What are the “objectlabs-system” and “objectlabs-system.admin.collections” collections?

These collections are created by mLab to store metadata about your deployment to service data browser features such as saved searches or table view definitions.

Are you PCI compliant?

mLab has satisfied the certification process for PCI DSS Merchant Compliance. This means that mLab adheres to the data security standards set by the Payment Card Industry (PCI) to ensure that credit card information remains safe and secure. Note that this compliance relates to mLab as a merchant and does not mean that mLab is PCI compliant to store credit card information.

Are you compliant with EU data protection standards and/or laws (e.g., GDPR, Privacy Shield)?

Please visit our documentation on EU Data Protection.

Do you have a REST API?

Yes, we do. However, it is not our recommended approach to connect to the database. You should only use the mLab Data API if you cannot use one of the standard MongoDB drivers.

Where do mLab-hosted databases get their time from?

mLab-hosted databases run on virtual machines that synchronize time from NTP.


I forgot the username and/or password for my mLab account

Use the form at to retrieve your password. You will be asked to enter the username for your account user (not to be confused with your mLab account name nor with a user in one of the databases you host with mLab). An email with a link to reset your password will be sent to the email address on file for that account user. If you do not receive an email, please double-check that you entered the correct username in the form.

If you do not remember the username for your account user, enter your email address in the form at If that email address matches any of the email addresses entered for account users in our system, an email will be sent which will include the mLab account name and the account user’s username.

If you do not receive the password reset or username reminder emails, please also check your spam or trash folders, in case your email system has automatically placed it there. It is also possible that the Admin User of your account has disabled the functionality which allows you to reset your password or recover your username. If you are not sure about this, please contact us at so that we can investigate the situation for you.

I can’t connect to my mLab database!

Are you finding yourself on the receiving end of an error message while trying to connect? Or is your application timing out? Our troubleshooting guide for connection issues may help you investigate possible causes.

Why am I getting the “Transaction numbers are only allowed on storage engines that support document-level locking” error?

This error indicates that your application is using is attempting to use a WiredTiger-only feature even though your mLab deployment is running on the MMAPv1 storage engine. mLab only supports the newer WiredTiger storage engine on its Dedicated plans.

The default for the retryWrites option in the connection string has changed to true in recent driver versions. As such it’s likely that you now have retryable writes enabled even though this feature is only supported on WiredTiger. Try setting retryWrites to false in your connection string or directly from your driver’s settings. If you still experience problems please contact us at for help.

My database seems slow—what do I do?

The performance and responsiveness of your database is affected by a variety of factors. First, it’s important to read MongoDB, Inc.’s comprehensive article, “MongoDB Performance”, which discusses the breadth of these factors.

In addition, we highly recommend that you read our Indexing and Performance page. Since proper indexing is a critical component in avoiding performance degradation, we discuss some very important indexing fundamentals and considerations here.

There is also the mLab Slow Query Analyzer which helps you discover potentially slow queries and implement recommended indexes. Note that this feature is available for for-pay plans only.