eXtremeDB vs RxDB

eXtremeDB is an in-memory database system designed for embedded devices and applications. It can combine in-memory and persistent storage within one database system. Interfaces include native APIs, REST, SQL, ODBC, and JDBC, with language APIs for C/C++, Java, Python, C#, Go, and Rust. For time-series data, a sequence type provides columnar storage. Distributed options include High Availability, Cluster, and Active Replication Fabric for replication across IoT tiers. Network communications can use TLS/SSL with OpenSSL or wolfSSL. Technical specifications list maximum database sizes of 4 GB on 32-bit architectures and 18.4 exabytes on 64-bit architectures. eXtremeDB supports Android, iOS, Linux, macOS, and Windows, and can be self-hosted. Evaluation downloads are listed for Linux, macOS, and Windows; custom trial packages can be requested for other platforms. McObject offers annual engineering support contracts that include software updates and a 50 percent discount on major upgrades. Commercial licensing is paid, with pricing available on request, and a 60-day trial is listed.

RxDB is a NoSQL database for JavaScript that runs inside an application and keeps data locally on the client. It supports offline operation, including applications that run entirely without a backend. When synchronization is needed, its Sync Engine connects to backends including RxServer, GraphQL, Firebase, Supabase, MongoDB, NATS, HTTP, CouchDB, WebRTC, Appwrite, Google Drive, and Microsoft OneDrive. Observable queries update as stored data changes. RxDB runs in browsers, mobile apps, desktop applications, and servers, with storage options including LocalStorage, IndexedDB, OPFS, SQLite, Node.js Filesystem, Expo Filesystem, MongoDB, and FoundationDB, among others. Collections use JSON Schema with validation and migration support. An encryption plugin protects locally stored documents with a password in browsers, React Native, and Node.js. The free tier is under Apache 2.0 and allows up to 13 open collections in parallel. Free users get community support through GitHub and Discord; Enterprise includes an SLA with a 24-hour first response. Pro costs $99 a month billed annually, and Pro Plus costs $239 a month billed annually.