WatermelonDB
WatermelonDB is a reactive database framework designed to build powerful React and React Native apps that scale from hundreds to tens of thousands of records while remaining fast. It ensures instant app launch regardless of data volume, supports lazy loading to load data only when needed, and offers offline-first capabilities with synchronization to your own backend. It is multiplatform. Optimized for React, it allows easy integration of data into components and is framework-agnostic, enabling the use of its JavaScript API with other UI frameworks. Built on a robust SQLite foundation, WatermelonDB provides static typing with Flow or TypeScript and optional reactivity through an RxJS API. WatermelonDB addresses performance issues in complex applications by loading nothing until requested and performing all querying directly on SQLite on a separate native thread, ensuring most queries resolve instantly.
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RxDB
RxDB is a local-first, NoSQL JavaScript database optimized for modern web and mobile applications. It enables offline-first functionality by storing data directly on the client using storage engines like IndexedDB, OPFS, SQLite, and more. RxDB offers real-time reactivity, allowing developers to subscribe to changes in documents, fields, or queries, ensuring that UI components update automatically as data changes. Its flexible replication engine supports syncing with various backends and custom endpoints. RxDB integrates seamlessly with frameworks and environments. Additional features include field-level encryption, schema validation, conflict resolution, backup and restore, attachments, and CRDT support. By reducing server load and providing low-latency local queries, RxDB enhances performance and scalability, making it ideal for applications that require real-time updates, offline access, and cross-platform consistency.
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Dexie
Dexie.js is a minimalistic and bulletproof IndexedDB wrapper library designed to simplify client-side storage. At only ~29k minified and gzipped, it offers a concise API that addresses the complexities of native IndexedDB, such as ambivalent error handling, poor queries, lack of reactivity, and code complexity. Dexie.js provides a well-thought-through API design, robust error handling, extendability, change tracking awareness, and extended KeyRange support, including case-insensitive search, set matches, and OR operations. It embraces the IndexedDB specification and all its features, allowing developers to use existing IndexedDB data without the need for data migration. Dexie.js supports composable real-time queries, enabling components to mirror the database in real-time across various front-end frameworks like React, Svelte, Vue, and Angular. With Dexie Cloud, developers can build consistent, authenticated, and access-controlled local-first apps with just a few lines of extra code.
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Realm
Realm is a mobile-first, open source object database designed to run directly inside phones, tablets, and wearables. It provides a simple, object-oriented data model that eliminates the need for an ORM, allowing developers to define models as regular classes in languages like Swift, Java, Kotlin, C#, JavaScript, Dart, and C++. Realm's architecture ensures high performance and low memory usage by employing a zero-copy design, lazy loading, and multi-version concurrency control (MVCC) for thread-safe operations. It's live objects and collections automatically update across threads, enabling reactive programming patterns. Realm supports relationships between objects via links and backlinks, facilitating complex data structures. Developers can utilize tools like Realm Studio to inspect and manipulate local Realm databases and integrate Realm into various platforms, including React Native, Flutter, Xamarin, and Node.js.
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