GIANT Stories at MongoDB

New to MongoDB Atlas — Global Clusters Enable Low-Latency Reads and Writes from Anywhere

The ability to replicate data across any number of cloud regions was introduced to MongoDB Atlas, the fully managed service for the database, last fall. This granted Atlas customers two key benefits. For those with geographically distributed applications, this functionality allowed them to leverage local replicas of their data to reduce read latency and provide a fast, responsive customer experience on a global scale. It also meant that an Atlas cluster could be easily configured to failover to another region during cloud infrastructure outages, providing customers with the ability to provision multi-region fault tolerance in just a few clicks.

But what about improving write latency and addressing increasingly demanding regulations, many of which have data residency requirements? In the past, users could address these challenges in a couple of ways. If they wanted to continue using a fully managed MongoDB service, they could deploy separate databases in each region. Unfortunately, this often resulted in added operational and application complexity. They could also build and manage a geographically distributed database deployment themselves and satisfy these requirements using MongoDB’s zone sharding capabilities.

Today we’re excited to introduce Global Clusters to MongoDB Atlas. This new feature makes it possible for anyone to effortlessly deploy and manage a single database that addresses all the aforementioned requirements. Global Clusters allow organizations with distributed applications to geographically partition a fully managed deployment in a few clicks, and control the distribution and placement of their data with sophisticated policies that can be easily generated and changed.

Improving app performance by reducing read and write latency

With Global Clusters, geographically distributed applications can write to (and of course, read from) local partitions of an Atlas deployment called zones. This new Global Writes capability allows you to associate and direct data to a specific zone, keeping it in close proximity to nearby application instances and end users. In its simplest configuration, an Atlas zone contains a 3-node replica set distributed across the availability zones of its preferred cloud region. This configuration can be adjusted depending on your requirements. For example, you can turn the 3-node replica set into multiple shards to address increases in local write throughput. You can also distribute the secondaries within a zone into other cloud regions to enable fast, responsive read access to that data from anywhere.

The illustration above represents a simple Global Cluster in Atlas with two zones. For simplicity’s sake, we’ve labeled them blue and red. The blue zone uses a cloud region in Virginia as the preferred region, while the red zone uses one in London. Local application instances will write to and read from the MongoDB primaries located in the respective cloud regions, ensuring low latency read and write access. Each zone also features a read-only replica of its data located in the cloud region of the other one. This ensures that users in North America will have fast, responsive read access to data generated in Europe, and vice versa.

Satisfying data residency for regulatory requirements

By allowing developers to easily direct the movement of data at the document level, Global Clusters provide a foundational building block that helps organizations achieve compliance with regulations containing data residency requirements. Data is associated with a zone and pinned to that zone unless otherwise configured.

The illustration below represents an Atlas Global Cluster with 3 zones — blue, red, and orange. The configuration of the blue and red zones are very similar to what we already covered. Local application instances read and write to nearby primaries located in the preferred regions — Virginia and London — and each zone includes a read-only replica in the preferred cloud region of every other zone for serving fast, global reads. What’s different is the orange zone, which serves Germany. Unlike data generated in North America and the UK, data generated in and around Germany is not replicated globally; instead, it remains pinned to the preferred cloud region located in Frankfurt.

Deploying your first Global Cluster

Now let’s walk through how easy it is to set up a Global Cluster with MongoDB Atlas.

In the Atlas UI, when you go to create a cluster, you’ll notice a new accordion labelled Global Cluster Configuration. If you click into this and enable “Global Writes”, you’ll find two easy-to-use and customizable templates. Global Performance provides reasonable read and write latency to the majority of the global population and Excellent Global Performance provides excellent read and write latency to majority of the global population. Both options are available across AWS, Google Cloud Platform, and Microsoft Azure.

You can also configure your own zones. Let’s walk through the setup of a Global Cluster using the Global Performance template on AWS. After selecting the Global Performance template, you’ll see that the Americas are mapped to the North Virginia region, EMEA is mapped to Frankfurt, and APAC is mapped to Singapore.

As your business requirements change over time, you are able to switch to the Excellent Global Performance template or fully customize your existing template.

Customizing your Global Cluster

Say you wanted to move your EMEA zone from Frankfurt to London. You can do so in just a few clicks. If you scroll down in the Create Cluster Dialog, you’ll see the Zone configuration component (pictured below). Select the zone you want to edit and simply update the preferred cloud region.

Once you’re happy with the configuration, you can verify your changes in the latency map and then proceed to deploy the cluster.

After your Global Cluster has been deployed, you’ll find that it looks just like any other Atlas cluster. If you click into the connect experience to find your connection string, you’ll find a simple and concise connection string that you can use in all of your geographically distributed application instances.

Configuring data for a Global Cluster

Now that your Global Cluster is deployed, let's have a look at the Atlas Data Explorer, where you can create a new database and collection. Atlas will walk you through this process, including the creation of an appropriate compound shard key — the mechanism used to determine how documents are mapped to different zones.

This shard key must contain the location field. The second field should be a well-distributed identifier, such as userId. Full details on key selection can be found in the MongoDB Atlas docs.

To help show what documents might look like in your database, we’ve added a few sample documents to a collection in the Data Explorer. As you can see above, we’ve included a field called location containing a ISO-3166-1 alpha 2 country code ("US", "DE", "IN") or a supported ISO-3166-2 subdivision code ("US-DC", "DE-BE", "IN-DL"), as well as a field called userId, which acts as our well-distributed identifier. This ensures that location affinity is baked into each document.

In the background, MongoDB Atlas will have automatically placed each of these documents in their respective zones. The document corresponding to Anna Bell will live in North Virginia and the document corresponding to John Doe will live in Singapore. Assuming we have application instances deployed in Singapore and North Virginia, both will use the same MongoDB connection string to connect to the cluster. When Anna Bell connects to our application from the US, she will automatically be working with data kept in close proximity to her. Similarly, when John Doe connects from Australia, he will be writing to the Singapore region.

Adding a zone to your Global Cluster

Now let’s say that you start to see massive adoption of your application in India and you want to improve the performance for local users. At anytime, you can return to your cluster configuration, click “Add a Zone”, and select Mumbai as the preferred cloud region for the new zone.

The global latency map will update, showing us the new zone and an updated view of the countries that map to it. When we deploy the changes, the documents that are tagged with relevant ISO country codes will gracefully be transferred across to the new zone, without downtime.

Scaling write throughput in a single zone

As we mentioned earlier in this post, it’s possible to scale out a single zone to address increases in local write throughput. Simply scroll to the “Zone Configuration”, click on “Additional Options” and increase the number of shards. By adding a second shard to a zone, you are able to double your write throughput.

Low-latency reads of data originating from other zones

We also referenced the ability to distribute read-only replicas of data from a zone into the preferred cloud regions of other zones, providing users with low-latency read access to data originating from other regions. This is easy to configure in MongoDB Atlas. In “Zone Configuration”, select “Add secondary and read-only regions”. Under “Deploy read-only replicas”, select “Add a node” and choose the region where you’d like your read-only replica to live.

For global clusters, Atlas provides a shortcut to creating read-only replicas of each zone in every other zone. Under “Zone configuration summary”, simply select the “Configure local reads in every zone” button.

MongoDB Atlas Global Clusters are very powerful, making it possible for practically any developer or organization to easily deploy, manage, and scale a distributed database layer optimized for low-latency reads and writes anywhere in the world. We're very excited to see what you build with this new functionality.

Global clusters are available today on Amazon Web Services, Google Cloud Platform, and Microsoft Azure for clusters M30 and larger.

Introducing Free Cloud Monitoring for MongoDB

With the release of MongoDB 4.0, we’re excited to announce the availability of free cloud monitoring, the easiest way to monitor and visualize the status of your MongoDB deployments.

There are no agents to install, no forms to fill out, no sign-ups necessary.

Let’s walk through how it works.

After you’ve installed MongoDB 4.0, connect to your instance(s) using the mongo shell, the interactive JavaScript interface to MongoDB. You should see the following message.

MongoDB shell version v4.0.0
connecting to: mongodb://
MongoDB server version: 4.0.0
Enable MongoDB's free cloud-based monitoring service to collect and display
metrics about your deployment (disk utilization, CPU, operation statistics,

The monitoring data will be available on a MongoDB website with a unique
URL created for you. Anyone you share the URL with will also be able to
view this page. MongoDB may use this information to make product
improvements and to suggest MongoDB products and deployment options to you.

To enable free monitoring, run the following command:

When you run the command, you should see something similar to what’s shown below.

    "state" : "enabled",
    "message" : "To see your monitoring data, navigate to the unique URL below. Anyone you share the URL with will also be able to view this page. You can disable monitoring at any time by running db.disableFreeMonitoring().",
    "url" : "",
    "userReminder" : "",
    "ok" : 1

Simply copy and paste your unique URL into a browser to access your monitoring dashboard. Free cloud monitoring tracks key performance indicators such as operation execution times, disk utilization, memory, network input/out, and more in interactive charts.

Mousing over chart lines reveal precise metrics.

You can also zoom in to 1 minute granularity.

Free cloud monitoring supports standalone instances and replica sets of MongoDB 4.0+. Of course, only monitoring metadata is accessed, never the contents of your databases. You can disable monitoring and your unique URL at any time by running the db.disableFreeMonitoring() command.

For more information, visit our documentation.

Get started with free cloud monitoring. Download MongoDB 4.0.

New to MongoDB Atlas — Free Fully Managed Databases on Google Cloud Platform

Today we’re excited to announce that the MongoDB Atlas free tier — which provides access to a fully managed M0 cluster with 512 MB of storage at no cost — is now available on Google Cloud Platform (GCP).

We launched the MongoDB Atlas database as a service on GCP one year ago at MongoDB World 2017. Since then, we’ve made significant product enhancements, culminating in the most powerful MongoDB service for developers building their applications on Google’s expanding ecosystem of cloud services. For example, we launched Atlas into 13 Google cloud regions earlier this year, and added the ability for customers to replicate their data to any number of regions for fast, responsive read access and multi-region fault tolerance.

Companies like Longbow Advantage, a supply chain partner to Del Monte Foods and Subaru of America, are using MongoDB Atlas on GCP to accelerate innovation and stay agile and efficient in their development life cycles.

We wanted to ensure that our team could remain focused on the application and not have to worry about the underlying infrastructure. Atlas allowed us to do just that.

Alex Wakefield, Chief Commercial Officer, Longbow Advantage

The availability of the Atlas free tier on GCP will make it easier than ever for developers using the cloud platform to experiment in an optimized environment for MongoDB, with no barrier to entry. The M0 cluster is ideal for learning MongoDB, prototyping, or early development, and has built-in security, availability, and fully managed upgrades.

The Atlas free tier on GCP is available in 3 regions:

  • Iowa (us-central1)
  • Belgium (europe-west1)
  • Singapore (asia-southeast1)

MongoDB Atlas is available in 13 GCP regions

Getting started is simple. When building a new cluster in MongoDB Atlas, select GCP as the cloud provider and then select the region closest to your application server(s) with the "Free tier available" label.

Then, in the Cluster Tier tab, select the M0 cluster size.

Finally, name your cluster.

That's it. We're excited to see what you build with MongoDB Atlas and GCP!

New to MongoDB Atlas — Fully Managed Connector for Business Intelligence

Driven by emerging requirements for self-service analytics, faster discovery, predictions based on real-time operational data, and the need to integrate rich and streaming data sets, business intelligence (BI) and analytics platforms are one of the fastest growing software markets.

Today, it’s easier than ever for MongoDB Atlas customers to make use of the MongoDB Connector for BI. The new BI Connector for Atlas is a fully managed, turnkey service that allows you to use your automated cloud databases as data sources for popular SQL-based BI platforms, giving you faster time to insight on rich, multi-structured data.

The BI Connector for Atlas removes the need for additional BI middleware and custom ETL jobs, and relies on the underlying Atlas platform to automate potentially time-consuming administration tasks such as setup, authentication, maintaining availability, and ongoing management.

Customers can use the BI Connector for Atlas along with the recently released MongoDB ODBC Driver to provide a SQL interface to fully managed MongoDB databases. This allows data scientists and business analysts responsible for analytics and business reporting on MongoDB data to easily connect to and use popular visualization and dashboarding tools such as Excel, Tableau, MicroStrategy, Microsoft Power BI, and Qlik.

When deploying the BI Connector, Atlas designates a secondary in your managed cluster as the data source for analysis, minimizing the likelihood an analytical workload could impact performance on your operational data store. The BI Connector for Atlas also utilizes MongoDB’s aggregation pipeline to push more work to the database and reduce the amount of data that needs to be moved and computed in the BI layer, helping deliver insights faster.

The BI Connector for Atlas is currently available for M10 Atlas clusters and higher.

New to MongoDB Atlas — Full CRUD Support in Data Explorer

As a fully managed database service, MongoDB Atlas makes life simpler for anyone interacting with MongoDB, whether you’re deploying a cluster on demand, restoring a snapshot, evaluating real-time performance metrics, or inspecting data.

Today, we’re taking it one step further by allowing developers to manipulate their data right from within the Atlas UI. The embedded Data Explorer, which has historically allowed you to run queries, view metadata regarding your deployments, and retrieve information such as index usage statistics, now supports full CRUD functionality.

To support these capabilities, new Project-level roles with different permission levels have been added.

You can assign users these new roles in the Users and Teams settings.

In addition, all Data Explorer operations are tracked and presented in the Atlas Activity Feed (found in the Alerts menu for each Project), allowing you to see who did what, and when.

When you click into the Data Explorer in Atlas, you should see new controls for interacting with your documents, collections, databases, and indexes. For example, modify existing documents using the intuitive visual editor, or insert new documents and clone or delete existing ones in just a few clicks. A comprehensive list of available Data Explorer operations can be found in the Atlas documentation.

The Data Explorer is currently available for M10 Atlas clusters and higher.

New to MongoDB Atlas on AWS — AWS Cloud Provider Snapshots, Free Tier Now Available in Singapore & Mumbai

AWS Cloud Provider Snapshots

MongoDB Atlas is an automated cloud database service designed for agile teams who’d rather spend their time building apps than managing databases, backups, and restores. Today, we’re happy to announce that Cloud Provider Snapshots are now available for MongoDB Atlas replica sets on AWS. As the name suggests, Cloud Provider Snapshots provide fully managed backup storage and recovery using the native snapshot capabilities of the underlying cloud service provider.

Choosing a backup method for a database cluster in MongoDB Atlas

When this feature is enabled, MongoDB Atlas will perform snapshots against the primary in the replica set; snapshots are stored in the same cloud region as the primary, granting you control over where all your data lives. Please visit our documentation for more information on snapshot behavior.

Cloud Provider Snapshots on AWS have built-in incremental backup functionality, meaning that a new snapshot only saves the data that has changed since the previous one. This minimizes the time it takes to create a snapshot and lowers costs by reducing the amount of duplicate data. For example, a cluster with 10 GB of data on disk and 3 snapshots may require less than 30 GB of total snapshot storage, depending on how much of the data changed between snapshots.

Cloud Provider Snapshots are available for M10 clusters or higher in all of the 15 AWS regions where you can deploy MongoDB Atlas clusters.

Consider creating a separate Atlas project for database clusters where a different backup method is required. MongoDB Atlas only allows one backup method per project. Once you select a backup method — whether it’s Continuous Backup or Cloud Provider Snapshots — for a cluster in a project, Atlas locks the backup service to the chosen method for all subsequent clusters in that project. To change the backup method for the project, you must disable backups for all clusters in the project, then re-enable backups using your preferred backup methodology. Atlas deletes any stored snapshots when you disable backup for a cluster.

Free, $9, and $25 MongoDB Atlas clusters now available in Singapore & Mumbai

We’re committed to lowering the barrier to entry to MongoDB Atlas and allowing developers to build without worrying about database deployment or management. Last week, we released a 14% price reduction on all MongoDB Atlas clusters deployed in AWS Mumbai. And today, we’re excited to announce the availability of free and affordable database cluster sizes in South and Southeast Asia on AWS .

Free M0 Atlas clusters, which provide 512 MB of storage for experimentation and early development, can now be deployed in AWS Singapore and AWS Mumbai. If more space is required, M2 and M5 Atlas clusters, which provide 2 GB and 5 GB of storage, respectively, are now also available in these regions for just $9 and $25 per month.

MongoDB 4.0 Release Candidate 0 Has Landed

MongoDB enables you to meet the demands of modern apps with a technology foundation that enables you through:

  1. The document data model – presenting you the best way to work with data.
  2. A distributed systems design – allowing you to intelligently put data where you want it.
  3. A unified experience that gives you the freedom to run anywhere – future-proofing your work and eliminating vendor lock-in.

Building on the foundations above, MongoDB 4.0 is a significant milestone in the evolution of MongoDB, and we’ve just shipped the first Release Candidate (RC), ready for you to test.

Why is it so significant? Let’s take a quick tour of the key new features. And remember, you can learn about all of this and much more at MongoDB World'18 (June 26-27).

Multi-Document ACID Transactions

Previewed back in February, multi-document ACID transactions are part of the 4.0 RC. With snapshot isolation and all-or-nothing execution, transactions extend MongoDB ACID data integrity guarantees to multiple statements and multiple documents across one or many collections. They feel just like the transactions you are familiar with from relational databases, are easy to add to any application that needs them, and and don't change the way non-transactional operations are performed. With multi-document transactions it’s easier than ever for all developers to address a complete range of use cases with MongoDB, while for many of them, simply knowing that they are available will provide critical peace of mind that they can meet any requirement in the future. In MongoDB 4.0 transactions work within a replica set, and MongoDB 4.2 will support transactions across a sharded cluster*.

To give you a flavor of what multi-document transactions look like, here is a Python code snippet of the transactions API.

with client.start_session() as s:
        collection.insert_one(doc1, session=s)
        collection.insert_one(doc2, session=s)

And now, the transactions API for Java.

try (ClientSession clientSession = client.startSession()) {
           try {
                   collection.insertOne(clientSession, docOne);
                   collection.insertOne(clientSession, docTwo);
          } catch (Exception e) {

Our path to transactions represents a multi-year engineering effort, beginning over 3 years ago with the integration of the WiredTiger storage engine. We’ve laid the groundwork in practically every part of the platform – from the storage layer itself to the replication consensus protocol, to the sharding architecture. We’ve built out fine-grained consistency and durability guarantees, introduced a global logical clock, refactored cluster metadata management, and more. And we’ve exposed all of these enhancements through APIs that are fully consumable by our drivers. We are feature complete in bringing multi-document transactions to replica sets, and 90% done on implementing the remaining features needed to deliver transactions across a sharded cluster.

Take a look at our multi-document ACID transactions web page where you can hear directly from the MongoDB engineers who have built transactions, review code snippets, and access key resources to get started.

Aggregation Pipeline Type Conversions

One of the major advantages of MongoDB over rigid tabular databases is its flexible data model. Data can be written to the database without first having to predefine its structure. This helps you to build apps faster and respond easily to rapidly evolving application changes. It is also essential in supporting initiatives such as single customer view or operational data lakes to support real-time analytics where data is ingested from multiple sources. Of course, with MongoDB’s schema validation, this flexibility is fully tunable, enabling you to enforce strict controls on data structure, type, and content when you need more control.

So while MongoDB makes it easy to ingest data without complex cleansing of individual fields, it means working with this data can be more difficult when a consuming application expects uniform data types for specific fields across all documents. Handling different data types pushes more complexity to the application, and available ETL tools have provided only limited support for transformations. With MongoDB 4.0, you can maintain all of the advantages of a flexible data model, while prepping data within the database itself for downstream processes.

The new $convert operator enables the aggregation pipeline to transform mixed data types into standardized formats natively within the database. Ingested data can be cast into a standardized, cleansed format and exposed to multiple consuming applications – such as the MongoDB BI and Spark connectors for high-performance visualizations, advanced analytics and machine learning algorithms, or directly to a UI. Casting data into cleansed types makes it easier for your apps to to process, sort, and compare data. For example, financial data inserted as a long can be converted into a decimal, enabling lossless and high precision processing. Similarly, dates inserted as strings can be transformed into the native date type.

When $convert is combined with over 100 different operators available as part of the MongoDB aggregation pipeline, you can reshape, transform, and cleanse your documents without having to incur the complexity, fragility, and latency of running data through external ETL processes.

Non-Blocking Secondary Reads

To ensure that reads can never return data that is not in the same causal order as the primary replica, MongoDB blocks readers while oplog entries are applied in batches to the secondary. This can cause secondary reads to have variable latency, which becomes more pronounced when the cluster is serving write-intensive workloads. Why does MongoDB need to block secondary reads? When you apply a sequence of writes to a document, then MongoDB is designed so that each of the nodes must show the writes in the same causal order. So if you change field "A" in a document and then change field "B", it is not possible to see that document with changed field "B" and not changed field "A". Eventually consistent systems suffer from this behavior, but MongoDB does not, and never has.

By taking advantage of storage engine timestamps and snapshots implemented for multi-document ACID transactions, secondary reads in MongoDB 4.0 become non-blocking. With non-blocking secondary reads, you now get predictable, low read latencies and increased throughput from the replica set, while maintaining a consistent view of data. Workloads that see the greatest benefits are those where data is batch loaded to the database, and those where distributed clients are accessing low latency local replicas that are geographically remote from the primary replica.

40% Faster Data Migrations

Very few of today’s workloads are static. For example, the launch of a new product or game, or seasonal reporting cycles can drive sudden spikes in load that can bring a database to its knees unless additional capacity can be quickly provisioned. If and when demand subsides, you should be able to scale your cluster back in, rightsizing for capacity and cost.

To respond to these fluctuations in demand, MongoDB enables you to elastically add and remove nodes from a sharded cluster in real time, automatically rebalancing the data across nodes in response. The sharded cluster balancer, responsible for evenly distributing data across the cluster, has been significantly improved in MongoDB 4.0. By concurrently fetching and applying documents, shards can complete chunk migrations up to 40% faster, allowing you to more quickly bring new nodes into service at just the moment they are needed, and scale back down when load returns to normal levels.

Extensions to Change Streams

Change streams, released with MongoDB 3.6, enable developers to build reactive, real-time, web, mobile, and IoT apps that can view, filter, and act on data changes as they occur in the database. Change streams enable seamless data movement across distributed database and application estates, making it simple to stream data changes and trigger actions wherever they are needed, using a fully reactive programming style.

With MongoDB 4.0, Change Streams can now be configured to track changes across an entire database or whole cluster. Additionally, change streams will now return a cluster time associated with an event, which can be used by the application to provide an associated wall clock time for the event.

Getting Started with MongoDB 4.0

Hopefully this gives you a taste of what’s coming in 4.0. There’s a stack of other stuff we haven’t covered today, but you can learn about it all in the resources below.

To get started with the RC now:

  1. Head over to the MongoDB download center to pick up the latest development build.
  2. Review the 4.0 release notes.
  3. Sign up for the forthcoming MongoDB University training on 4.0.

And you can meet our engineering team and other MongoDB users at MongoDB World'18 (June 26-27).


* Safe Harbor Statement

This blog post contains “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. Such forward-looking statements are subject to a number of risks, uncertainties, assumptions and other factors that could cause actual results and the timing of certain events to differ materially from future results expressed or implied by the forward-looking statements. Factors that could cause or contribute to such differences include, but are not limited to, those identified our filings with the Securities and Exchange Commission. You should not rely upon forward-looking statements as predictions of future events. Furthermore, such forward-looking statements speak only as of the date of this presentation.

In particular, the development, release, and timing of any features or functionality described for MongoDB products remains at MongoDB’s sole discretion. This information is merely intended to outline our general product direction and it should not be relied on in making a purchasing decision nor is this a commitment, promise or legal obligation to deliver any material, code, or functionality. Except as required by law, we undertake no obligation to update any forward-looking statements to reflect events or circumstances after the date of such statements.

Optimizing for Fast, Responsive Reads with Cross-Region Replication in MongoDB Atlas

MongoDB Atlas customers can enable cross-region replication for multi-region fault tolerance and fast, responsive reads.

  • Improved availability guarantees can be achieved by distributing replica set members across multiple regions. These secondaries will participate in the automated election and failover process should the primary (or the cloud region containing the primary) go offline.
  • Read-only replica set members allow customers to optimize for local reads (minimize read latency) across different geographic regions using a single MongoDB deployment. These replica set members will not participate in the election and failover process and can never be elected to a primary replica set member.

In this post, we’ll dive a little deeper into optimizing for local reads using cross-region replication and walk you through the necessary configuration steps on an environment running on AWS.

Primer on read preference

Read preference determines how MongoDB clients route read operations to the members of a replica set. By default, an application directs its read operations to the replica set primary. By specifying the read preference, users can:

  • Enable local reads for geographically distributed users. Users from California, for example, can read data from a replica located locally for a more responsive experience
  • Allow read-only access to the database during failover scenarios

A read replica is simply an instance of the database that provides the replicated data from the oplog; clients will not write to a read replica.

With MongoDB Atlas, we can easily distribute read replicas across multiple cloud regions, allowing us to expand our application's data beyond the region containing our replica set primary in just a few clicks.

To enable local reads and increase the read throughput to our application, we simply need to modify the read preference via the MongoDB drivers.

Enabling read replicas in MongoDB Atlas

We can enable read replicas for a new or existing MongoDB paid cluster in the Atlas UI. To begin, we can click on the cluster “configuration” button and then find the link named "Enable cross-region configuration options."

When we click this, we’ll be presented with an option to select the type of cross-replication we want. We'll choose deploy read-only replicas:

As you can see above, we have our preferred region (the region containing our replica set primary) set to AWS, us-east-1 (Virginia) with the default three nodes. We can add regions to our cluster configuration based on where we think other users of our application might be concentrated. In this case, we will add additional nodes in us-west-1 (Northern California) and eu-west-1 (Ireland), providing us with read replicas to serve local users.

Note that all writes will still go to the primary in our preferred region, and reads from the secondaries in the regions we’ve added will be eventually consistent.

We’ll click "Confirm and Deploy", which will deploy our multi-region cluster.

Our default connection string will now include these read replicas. We can go to the "Connect" button and find our full connection string to access our cluster:

When the deployment of the cluster completes, we will be ready to distribute our application's data reads across multiple regions using the MongoDB drivers. We can specifically configure readPreference within our connection string to send clients to the "closest replicas". For example, the Node native MongoDB Driver permits us to specify our preference:

readPreference Specifies the replica set read preference for this connection.

The read preference values are the following:

For our app, if we want to ensure the read preference in our connection string is set to the nearest MongoDB replica, we would configure it as follows:


Security and Connectivity (on AWS)

MongoDB Atlas allows us to peer our application server's VPC directly to our MongoDB Atlas VPC within the same region. This permits us to reduce the network exposure to the internet and allows us to use native AWS Security Groups or CIDR blocks. You can review how to configure VPC Peering here.

A note on VPCs for cross-region nodes:

At this time, MongoDB Atlas does not support VPC peering across regions. If you want to grant clients in one cloud region read or write access to database instances in another cloud region, you would need to permit the clients’ public IP addresses to access your database deployment via IP whitelisting.

With cross-region replication and read-only replicas enabled, your application will now be capable of providing fast, responsive access to data from any number of regions.

Get started today with a free 512 MB database managed by MongoDB Atlas here.

New to MongoDB Atlas — Live Migrate Sharded Clusters and Deployments Running MongoDB 2.6

Live migration in MongoDB Atlas enables users to import data from MongoDB deployments running in other environments and cut over to a fully managed database service, giving you industry best practice security by default, advanced features to streamline operations and performance optimization, and the latest versions of MongoDB.

Today, we’re introducing two new enhancements to MongoDB Atlas live migration that make it easier than ever for users to take advantage of the official cloud database service for MongoDB with minimal impact to their applications.

  • Previously, live migration could only be performed on a replica set running MongoDB version 3.0 and above. MongoDB Atlas now supports live migrations of replica sets running MongoDB 2.6, making it easier for users running older versions to transition to a fully managed service and a more recent version of the database software.
  • Live migrations will now also support sharded clusters, meaning that some of the world’s largest MongoDB workloads can now be moved to MongoDB Atlas with less effort and minimal impact to production applications.

Live migrate from MongoDB 2.6 to 3.2+

Upgrading to a new database version may seem like routine work for some, but, as battle-hardened IT operators know, can have complexities and require plenty of strategy and foresight.

Between all the applications and end users you have, the prospect of upgrading to a new release can be a major undertaking requiring significant planning. While some of our Enterprise and Community customers love to upgrade to the latest release as soon as possible to get new features and performance improvements, others take a more measured approach to upgrading.

To make upgrading easier, we are excited to announce that we have extended database version support for the live migration tool in MongoDB Atlas. MongoDB users running older versions of the database can now easily update to the latest versions of the database and migrate to the best way to run MongoDB in the cloud, all at the same time.

Using live migration, you can migrate from any MongoDB 2.6 replica set to a MongoDB 3.2+ cluster on Atlas. This requires no backend configuration, no downtime, and no upgrade scripting. Once our migration service is able to communicate with your database, it will do all the heavy lifting.

The migration service works by:

  • Performing a sync between your source database and a target database hosted in MongoDB Atlas
  • Syncing live data between your source database and the target database by tailing the oplog
  • Notifying you when it’s time to cut over to the MongoDB Atlas cluster

Given that you’re upgrading a critical part of your application, you do need to be wary of how your application’s compatibility with the database might change, and for that we recommend the following stages are included in your upgrade plan:

  • Upgrade your application to make use of the latest MongoDB drivers, and make any necessary code changes
  • Create a staging environment on MongoDB Atlas
  • Use the live migration tool to import your data from your existing MongoDB replica
  • Deploy a staging version of your updated application and connect it to your newly created MongoDB Atlas staging environment
  • Perform thorough functional and performance tests to ensure behavior is as expected
  • Re-use the live migration tool to import your production data when ready, and then perform the hard cutover in databases and application versions
Compatibility between source and destination cluster versions.

Live migrate sharded clusters

Until today, migrating a sharded MongoDB deployment with minimal downtime has been difficult. The live migration tool now makes this possible for customers looking to move their data layer into MongoDB Atlas.

When performing a live migration on a sharded cluster, we recommend that in addition to following the process listed above, that you also consider the following:

  • Our live migration service will need access to all your shards and config servers, in addition to your mongos servers
  • You can only migrate across like database versions e.g. 3.2 to 3.2, 3.4 to 3.4, etc.
  • You must migrate from and to the same number of shards
  • For full details on sharded live migrations, click here

Ready to migrate to MongoDB Atlas? Get started here.

New to MongoDB Atlas — Cloud Provider Snapshots on Azure, Expanded API for Snapshots and Restore Jobs

Leo Zheng
February 14, 2018
Release Notes, Cloud

One of the core components of MongoDB Atlas, the cloud database service for MongoDB, is the fully managed disaster recovery functionality. With continuous backups, you can take consistent, cluster-wide snapshots of sharded deployments and trigger point-in-time restores to satisfy demanding recovery point objectives (RPOs) from the business. Continuous backups also allow you to query backup snapshots to restore granular data in a fraction of the time it would take to restore an entire snapshot.

Today we’re making it even easier to manage your backups with an expanded Atlas API. Programmatically get metadata about your snapshots, delete them, or change their expiration. Trigger restore jobs and retrieve them. The MongoDB Atlas API allows you to incorporate the rich functionality of Atlas fully managed backups into workflows optimized for how you manage your IT resources.

Visit our documentation for more information.

Cloud Provider Snapshots for Azure

We are also introducing a new type of managed backup service for MongoDB Atlas, using the native snapshot capabilities of your cloud provider. With cloud provider snapshots, your backups will be stored in the same cloud region as your managed databases, granting you better governance over where all of your data lives.

For deployments using cross-region replication, your backups will be stored in your preferred region.

Compared to continuous backups, cloud provider snapshots allow for fast restores of snapshot images. Pricing, which varies slightly from region to region, is also lower.

Cloud provider snapshots are available today for replica sets on Microsoft Azure. Support for Amazon Web Services and Google Cloud Platform will be rolled out later this year.

If you’re considering switching backup methods (from continuous backup to cloud provider snapshots), consider creating a separate project in MongoDB Atlas. For each Atlas project, the first cluster you enable backups for will dictate the backup method for all subsequent clusters in the project. To change the backup method within the same the project, disable backups for all clusters in the project, then re-enable backups using your preferred backup methodology. MongoDB Atlas automatically deletes any stored snapshots when you disable backups for a cluster.

Not yet a MongoDB Atlas user? Create an account and get a free 512 MB database.