eXist-db vs JayDB

eXist-db is a free, open-source NoSQL document database and application platform centered on XML. Its native engine stores textual or binary documents without requiring a database schema, and it is designed for self-hosted deployment on Linux, macOS, or Windows. The product implements XQuery 3.1, though some features and functions are unsupported, and RESTXQ lets developers deploy RESTful services from XQuery annotations. Its interfaces include REST-style HTTP, SOAP, XML-RPC, and WebDAV. A browser-based IDE provides syntax coloring, code completion, and error checking for application artifacts. Full-text search uses an implementation-specific Apache Lucene approach rather than the W3C XQuery and XPath Full Text 3.0 specification. Security extends Unix permissions with access control lists and external authentication realms. The software is licensed under the LGPL for academic, non-commercial, and commercial use. The documentation lists Java 8 for versions 3.x–6.x or Java 21 for version 7.x, about 500 MB of disk space, and at least 512 MB of memory.

JayDB is a JSON document database with per-user sign-in, aimed at static apps that need user, session, or tenant data without an app-owned backend. Documents are JSON at slash-separated paths, and the first write creates the namespace. Its REST data plane supports GET, PUT, DELETE, and prefix listing. Browser apps can authenticate through OIDC with Authorization Code and PKCE without embedding a client secret. Listed identity providers include Google, GitHub, Microsoft, generic OIDC, and custom OAuth2. The official SDK supports authentication, token refresh, typed document access, and compare-and-swap operations. ETag-based compare-and-swap may reject a write with HTTP 412 if the document changed since it was read. JayDB is available as managed cloud software or as a self-hosted Go engine under the MIT license, using S3-compatible storage or local disk. The free plan is free and includes 1 GB stored, 100,000 reads per month, and 10,000 writes per month; usage hard-stops at those allowances. Metered rates are $0.05 per GB-month of storage, $0.20 per million reads, and $0.50 per million writes.