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| Realm (database) | |
|---|---|
| Name | Realm |
| Developer | MongoDB, Inc. |
| Released | 2014 |
| Programming language | C++, Java, Swift, Objective-C, Kotlin |
| Operating system | Android, iOS, Linux, macOS, Windows |
| License | Server Side Public License; Apache License 2.0 (historical) |
Realm (database) Realm is a cross-platform mobile and embedded database engine designed for local storage and synchronization in Android, iOS, and desktop applications. Initially developed by an independent company and later acquired by MongoDB, Inc., Realm provides object-oriented APIs, a reactive change-notification system, and synchronization capabilities that integrate with cloud services and enterprise backends. The project emphasizes low-latency local reads and writes, predictable memory usage, and tight integration with native application stacks such as Swift, Objective-C, Java, and Kotlin.
Realm originated as a startup product introduced in 2014 targeting mobile developers seeking alternatives to SQLite and Core Data. Early coverage compared Realm to established technologies in the context of performance and developer ergonomics amid growing mobile ecosystems on iPhone and Android platforms. In 2019, Realm and its synchronization technology were acquired by MongoDB, Inc., aligning the project with MongoDB's portfolio of database products and cloud services such as MongoDB Atlas and strategic initiatives around offline-first applications. The acquisition followed trends in database consolidation visible in prior consolidations like MySQL AB acquisition by Sun Microsystems and later changes in open-source licensing models exemplified by moves from companies such as Redis Labs.
Realm's core is implemented in C++ to provide a compact, high-performance engine embeddable in native applications across Android and iOS. The architecture separates a local storage engine, object mapping layers for languages like Swift and Java, and an optional synchronization service that coordinates with cloud components. Key components include the core database file, language-specific SDKs, a sync protocol, and tooling for schema migrations and change notifications. The sync component was developed to interoperate with cloud backends including MongoDB Atlas, third-party services, and custom servers, reflecting approaches seen in systems such as CouchDB and Apache CouchDB replication.
Realm uses an object-oriented, schema-defined data model where persistent types are declared as classes or structs in host languages like Swift and Kotlin. APIs expose read and write transactions, live objects that update in-place, query builders, and notification tokens that enable reactive UI updates in frameworks such as UIKit and Jetpack Compose. Query capabilities include predicate-style filters and sorting comparable to query interfaces in Core Data and LINQ-like patterns familiar from .NET Framework. SDKs provide synchronous and asynchronous APIs, change listeners for fine-grained updates, and migration hooks for evolving schemas during application updates.
Realm emphasizes low-latency access by using memory-mapped files, copy-on-write semantics, and zero-copy object access patterns derived from designs seen in high-performance systems like LMDB and LevelDB. Benchmarks published in community discussions compared Realm's single-threaded and multithreaded performance to SQLite and Core Data for common mobile workloads. For larger datasets and multi-user scenarios, scalability depends on partitioning, sync throughput, and cloud backend capacity such as that provisioned by MongoDB Atlas clusters or custom sync servers. Realm's architecture supports sharding-like patterns via partition keys and integrates with horizontal scaling strategies used by distributed databases including Cassandra and CockroachDB at the backend layer.
Realm's synchronization stack provides conflict resolution policies, end-to-end encryption options, and integration with authentication providers including OAuth 2.0 flows and identity platforms used by Google (company), Apple Inc., and enterprise identity systems. Sync implements client-side encryption and server-side access controls when paired with cloud backends, and supports offline-first conflict handling with last-write-wins or application-driven merges akin to strategies in CRDT research and systems like Dropbox synchronization. Security posture and licensing changes after acquisition influenced deployment patterns similar to industry reactions to license revisions by Red Hat and other vendors.
Realm is used broadly in mobile applications for offline-first experiences, local caching, real-time collaboration, and telemetry collection in sectors represented by companies such as Uber Technologies, Inc., Instagram, Airbnb, and other consumer-facing platforms that prioritize responsive UI and synchronization. Developers choose Realm for features like live objects, reactive notifications, and seamless sync to cloud backends such as MongoDB Atlas or bespoke services used in enterprises like Salesforce and Microsoft Corporation deployments. Educational projects, open-source tools, and startups also adopted Realm in prototypes and production apps where rapid iteration and native-language APIs were priorities.
Realm's licensing evolved over time: the core engine and SDKs were historically available under permissive terms, while server-side components and synchronization services moved under proprietary or server-side licenses following the acquisition by MongoDB, Inc.. The ecosystem includes official SDKs for Swift, Objective-C, Java, Kotlin, and community-maintained bindings for other environments. Integration tooling, migration libraries, and third-party extensions exist in repositories and package managers associated with GitHub, CocoaPods, Maven Central, and npm. The project's trajectory mirrors patterns in open-source ecosystems where corporate stewardship, community contributions, and commercial services intersect, comparable to evolutions seen with Elastic NV and other database vendors.
Category:Databases