RxDB

Overview

RxDB is a JavaScript NoSQL database that runs in the application, keeping data on the client and supporting offline use. It is best suited to developers building apps that need local data, live queries and a choice of synchronization targets. Its breadth is compelling, but the Free tier’s 13-open-collection limit and the differences between storage options deserve attention before committing.

Key features

RxDB can keep an app working without a network connection, and can run entirely without a backend. When data must be shared, its Sync Engine supports connections to services including RxServer, GraphQL, Firebase, Supabase, MongoDB, CouchDB, WebRTC, Appwrite, Google Drive and Microsoft OneDrive. That range can accommodate varied architectures, though teams still need to choose storage and synchronization approaches that fit their app.

Observable queries react to stored-data changes, which suits interfaces that need current results without relying on manual refreshes. Collections use JSON Schema, with validation and migration support for managing data structure changes. A password-based encryption plugin protects locally stored documents and works in browsers, React Native and Node.js.

Storage options cover browser, mobile, desktop and server use, including IndexedDB, OPFS, SQLite, Node.js Filesystem, MongoDB and FoundationDB. LocalStorage is meant for simple browser setups and very small datasets, not large volumes or heavy writes. Choosing it for a demanding workload would undercut the advantages of the broader storage menu.

Deployed applications do not send requests from users to an RxDB server, and premium plugins contain no tracking code. That is useful for teams concerned about production privacy, while leaving them responsible for their own app and backend design.

Pricing

The Free plan costs free, billed forever, and includes RxDB core, replication and realtime sync, default storages, community support, and up to 13 open collections in parallel. It is a practical starting point for small projects, but the collection cap can constrain apps that need many simultaneously open collections. The free tier uses the Apache 2.0 license, and support is through GitHub and Discord. There is no free trial.

Pro costs $99 a month, billed annually, with unlimited developers. It adds OPFS, IndexedDB, SQLite and Filesystem storage, plus WebCrypto Encryption and Fulltext Search. This is the clearest upgrade for teams needing those storage choices or features beyond the Free plan.

Pro Plus costs $239 a month, billed annually, also with unlimited developers. It adds Worker and Shared Worker storage, sharding, memory-mapped storage, optimizers, Fastify/Koa adapters and a Sentry-compatible logger. Those additions make it the fit for projects that need these advanced capabilities rather than a general-purpose step up for every team.

Enterprise has custom pricing and includes a custom commercial license, a named engineer, a 24-hour first-response support SLA, architecture review, priority fixes and source-code access. It is aimed at organizations that need contracted support and direct engineering access.

Platforms

RxDB runs in browsers, mobile apps, desktop applications and servers. Its supported platforms include Android, iOS, Linux, macOS, Windows, web, API and self-hosted environments, giving JavaScript teams options across client and server deployments.

Who it's for

RxDB is a strong fit for developers building JavaScript apps that need local-first behavior, offline operation, reactive queries or synchronization across multiple backend choices. Teams should compare storage requirements and collection counts against the plan limits before choosing it. It is less suitable for someone seeking a ready-made consumer app rather than a database for application development, or for a project that would rely on LocalStorage for substantial data or frequent writes.

Pros and cons

• Pro: Offline operation can work with or without a backend, supporting apps that must remain useful without connectivity.
• Pro: A broad set of synchronization targets and storage options gives development teams room to match the database to different runtimes and architectures.
• Pro: Reactive queries, JSON Schema validation and migrations support responsive interfaces and managed schema changes.
• Pro: The Free plan is billed forever, and the Apache 2.0 license gives teams a no-cost way to begin.
• Con: Free is capped at 13 open collections in parallel, which may force an upgrade as an app’s needs grow.
• Con: LocalStorage is unsuitable for large datasets and heavy writes, so storage selection matters to performance and scale.
• Con: Pro and Pro Plus are billed annually despite monthly price presentation, so the listed monthly rate is not a month-to-month term.

Alternatives

For a broader comparison, browse Mobile Databases or Embedded Databases.

Consider Espresso instead if the need is Android UI testing: its free plan targets a single app and supports Android 4.0.1/API 14 and later. Hive is another free option, with a free tier that includes 200MB storage and up to 10 workspace members. Choose Ditto if its cloud-connected device model fits better; its Free plan includes 10 cloud device connections, 2GB storage and 5GB data transfer, but no SLA and limited support.

ObjectBox offers a no-cost core database, making it worth considering when fundamental database capabilities are enough; its Sync plan has a separate price. Realm is a free alternative; MongoDB acquired the technology and renamed it MongoDB Atlas Device SDKs in 2023. Sparksee may fit academic use, with a free academic licence requiring a valid school or university ID. SQLDelight is a free open-source Kotlin SQL code-generation library, while WCDB is a free open-source mobile database framework.

Verdict

Choose RxDB if you are building a JavaScript application that needs local-first data, offline operation and flexible synchronization or storage choices. The combination of reactive queries and runtime breadth makes it particularly adaptable, while the free collection cap and annual billing on paid plans should figure into project planning. Look elsewhere if you need a turnkey app or expect to depend on LocalStorage for large or write-heavy data.