Introducing MongoDB Realm’s Flexible Sync – Now Available in Preview

Emma Lullo and Ian Ward
January 24, 2022 | Updated: October 11, 2024

>> Announcement: Some features mentioned below will be deprecated on Sep. 30, 2025. Learn more.

Twelve months ago, we made MongoDB’s edge-to-cloud data synchronization service, Realm Sync, generally available. Since then, Sync has helped hundreds of our customers build reliable, offline-first mobile apps that serve data to millions of end users – from leading telematics providers to chart-topping consumer apps.

Historically, Realm Sync has worked well for apps where data is compartmentalized and permissions rarely change, but dynamic use cases with evolving permissions required workarounds. We knew we could do more, so today we are excited to announce the next iteration of Realm Sync – Flexible Sync. With the introduction of Flexible Sync, we are redefining the sync experience by enabling even the most complex use cases out-of-the-box without requiring any custom code.

Intuitive query-based sync

Distinctly different from how Realm Sync operates today, Flexible Sync lets you use language-native queries to define the data synced to user applications. This more closely mirrors how you are used to building applications today – using GET requests with query parameters – making it easy to learn and fast to build to MVP.

Flexible Sync also supports dynamic, overlapping queries based on user inputs. Picture a retail app that allows users to search available inventory. As users define inputs – show all jeans that are size 8 and less than $40 – the query parameters can be combined with logical ANDs and ORs to produce increasingly complex queries, and narrow down the search result even further.

In the same application, employees can quickly limit inventory results to only their store’s stock, pulling from the same set of documents as the customer, without worrying about overlap.

Document-level permissions

Whether it’s a company’s internal application or an app on the App Store, permissions are required in almost every application. That’s why we are excited by how seamless Flexible Sync makes applying a document-level permission model when syncing data – meaning synced documents can be limited based on a user’s role.

Consider how an emergency room team would use their hospital’s application. A resident should only be able to access her patients’ charts while her fellow needs to be able to see the entire care team’s charts. In Flexible Sync, a user’s role will be combined with the client-side query to determine the appropriate result set. For example, when the resident above filters to view all patient charts the permission system will automatically limit the results to only her patients.

Real-time collaboration optimizations

Flexible Sync also enhances query performance and optimizes for real-time collaboration by treating a single object or document as the smallest entity for synchronization. This means synced data is shared between client devices more efficiently and conflict resolution incorporates changes faster and with less data transfer than before.

Getting started

Flexible Sync is available now. Simply sign up or log in to your cloud account, deploy a Realm app, select your sync type, and dive right in.

Flexible Sync is compatible with MongoDB 5.0, which is available with dedicated Atlas database clusters (M10 and higher). Shared-tier cluster support for 5.0 and Flexible Sync will be made available mid-February.

Have questions? Check out our documentation or the more detailed announcement post on the Developer Hub.

Looking ahead

Our goal with Flexible Sync is to deliver a sync service that can fit any use case or schema design pattern imaginable without custom code or workarounds. And while we are excited that Flexible Sync is now in preview, we’re nowhere near done.

The Realm Sync team is planning to bring you more query operators, permissions integrations, and enhancements over the course of 2022. We look to you, our users, to help us drive the roadmap. Submit your ideas and feature requests to our feedback portal and ask questions in our Community forums. Happy building!

← Previous

10 Signs Your Data Architecture Is Limiting Your Innovation: Part 3

When it comes to your database architecture, complexity can quickly lead to a drag on your productivity, frustration for your developers, and less time to focus on innovation while your team maintains the status quo. New feature rollouts take longer than they should, while your resources are consumed up by tedious tasks that allow your app to survive, but not truly thrive. This complexity manifests in many different ways; as they accumulate, they can become a serious hindrance to your ability to bring innovative ideas to market. We think of the effect as a kind of tax — a tax that is directly rooted in the complexity of your data architecture. We call it DIRT — the Data and Innovation Recurring Tax . We have identified ten symptoms that can indicate your business is paying DIRT. For an in-depth view, read our white paper 10 Signs Your Data Infrastructure is Holding You Back . Sign #5: New features are rolled out in months, not days With a complex data architecture, your developers have to switch constantly between languages and think in different frameworks. They may use one language to work directly with a database, another to use the object-relational mapping (ORM) layer built on top of it, and yet another to access search functionality. That becomes a major drag on productivity. That slows down your individual developers, but it also has consequences for how they work as a team. If every application architecture is bespoke, it’s almost impossible for developers’ skills to be shared and put to use across an organization. Development slows down. When a key person leaves, there is no one who can effectively fill in and you end up hiring for very specific skills. That’s hard enough, but you also don’t know if you’ll still need those skills in a year or three. Sign #6: It takes longer to roll out schema changes than to build new features If you’re rolling out application changes frequently — or trying to — and you’re using a relational database, then schema changes are hard to avoid. One survey found that 60% of application changes require modifications to existing schema, and, worse, those database changes take longer to deploy than the application changes they are supposed to support. Legacy relational databases require developers to choose a schema at the outset of a project, before they understand the entirety of the data they need or the ways in which their applications will be used. Over time, and with user feedback, the application takes shape — but often it’s not the shape that was originally anticipated. At that point, a fixed schema makes it very hard to iterate, leaving teams with a tough choice: try to achieve your new goals within the context of a schema that isn’t really suitable or go through the painful process of changing it. Learn more about the innovation tax and how to lessen it in our white paper DIRT and the High Cost of Complexity .

January 21, 2022

Next →

MongoDB’s 2024 Year in Review

It’s hard to believe that another year is almost over! 2024 was a transformative year for MongoDB, and it was marked by both innovation and releases that further our commitment to empowering customers, developers, and partners worldwide. So without further ado, let’s dive into MongoDB’s 2024 highlights. We’ll also share our executive team’s predictions of what 2025 might have in store. A look back at 2024 MongoDB 8.0: The most performant version of MongoDB ever In October we released MongoDB 8.0 , the fastest, most resilient, secure, and reliable version of MongoDB yet. Architectural optimizations in MongoDB 8.0 have significantly improved the database’s performance, with 36% faster reads and 59% higher throughput for updates. Our new architecture also makes horizontal scaling cheaper and faster. Finally, working with encrypted data is easier than ever, thanks to the addition of range queries in Queryable Encryption (which allows customers to encrypt, store, and perform queries directly on data). Whether you’re a startup building your first app, or you’re a global enterprise managing mission-critical workloads, MongoDB 8.0 offers unmatched power and flexibility, solidifying MongoDB’s place as the world’s most popular document database. Learn more about what makes 8.0 the best version of MongoDB ever on the MongoDB 8.0 page . Delivering customer value with the MongoDB AI Applications Program AI applications have become a cornerstone of modern software, and MongoDB is committed to equipping customers with the technology, tools, and support they need to succeed on their AI journey. That’s why we launched the MongoDB AI Applications Program (MAAP) in 2024, a comprehensive program designed to accelerate the development of AI applications. By offering customers resources like access to AI specialists, an ecosystem of leading AI and tech companies, and AI architectural best practices supported by integrated services, MAAP helps solve customers’ most pressing business challenges, unlocks competitive advantages, and accelerates time to value for AI investments. Overall, MAAP’s aim is to set customers on the path to AI success. Visit the MongoDB AI Applications Program page or watch our session from AWS re:Invent to learn more! Advancing AI with MongoDB Atlas Vector Search In 2024, MongoDB further cemented its role in the AI space with enhancements to MongoDB Atlas Vector Search . Recognized in 2024 (for the second consecutive year!) as one of the most loved vector databases , MongoDB continues to provide a scalable, unified, and secure platform for building cutting-edge AI use cases. Recent advancements like vector quantization in Atlas Vector Search help deliver even more value to our customers, enabling them to scale applications to billions of vectors at a lower cost. Head over to our Atlas Vector Search quick start guide to get started with Atlas Vector Search today, or visit our AI resources hub to learn more about how MongoDB can power AI applications. Search Nodes: Performance at scale Search functionality is indispensable in modern applications, and with Atlas Search Nodes, organizations can now optimize their search workloads like never before. By providing dedicated infrastructure for Atlas Search and Vector Search workloads, Search Nodes ensure high performance (e.g., a 40–60% decrease in query times), scalability, and reliability, even for the most demanding use cases. As of this year , Search Nodes are generally available across AWS, Google Cloud, and Microsoft Azure. This milestone underscores MongoDB’s commitment to delivering powerful solutions that scale alongside our customers’ needs. To learn more about Search Nodes, check out our documentation or watch our tutorial . Looking ahead: MongoDB’s 2025 predictions After the excitement of the past few years, 2025 will be defined by ensuring that technology investments deliver tangible value. Organizations remain excited about the potential AI and emerging technologies hold to solve real business challenges, but are increasingly focused on maintaining a return on investment. “Enterprises need to innovate faster than ever, but speed is no longer the only measure of success. Increasingly, organizations are laser-focused on ensuring that their technology investments directly address critical business challenges and provide clear ROI and competitive advantage—whether it’s optimizing supply chains, delivering hyper-personalized customer experiences, or scaling operations efficiently,” said Sahir Azam, Chief Product Officer at MongoDB. “In 2025, I expect to see organizations make significant strides in driving this innovation and efficiency by applying AI to more production use cases and by maturing the way they leverage their data to build compelling and differentiated customer experiences.” Indeed, we expect to see organizations make more strategic investments in emerging technologies like gen AI—innovating with a sharp focus on solving business challenges. “In 2025, we can expect the focus to shift from ‘what AI can do’ to ‘what AI should do,’ moving beyond the hype to a clearer understanding of where AI can provide real value and where human judgment is still irreplaceable,” said Tara Hernandez, VP of Developer Productivity at MongoDB. “As we advance, I think we’ll see organizations begin to adopt more selective, careful applications of AI, particularly in areas where stakes are high, such as healthcare, finance, and public safety. A refined approach to AI development will be essential—not only for producing quality results but also to build trust, ensuring these tools genuinely support human goals rather than undermining them.” With more capable, accessible application development tools and customer-focused programs like MAAP at developers’ fingertips, 2025 is an opportunity to make a data-driven impact faster than ever before. "Right now, organizations have an opportunity to leverage their data to reimagine how they do business, to more effectively adapt to a changing world, and to revolutionize our quality of life,” said Andrew Davidson, SVP of Products at MongoDB. “By harnessing our latest technologies, developers can build a foundation for a transformative future." Head over to our updates page to learn more about the new releases and updates from MongoDB in 2024. Keep an eye on our events page to learn what's to come from MongoDB in 2025!

December 19, 2024