HSQLDB

vs

CouchDB

PouchDB is a free and open-source JavaScript database inspired by Apache CouchDB. The database is designed from the ground-up to run well within modern web browsers. With PouchDB you can create web applications that works as well offline as they do online. PouchDB achives this by storing data locally, then synchronize it with CouchDB and compatible servers when the user get internet access once again. This is especially useful for applications facing countries and regions with lower quality internet connections or unstable infrastructure.

PostgreSQL, or Postgres for short is a widely popular, free and open-source relational database management system. PostgreSQL is available for all major operating systems including macOS, Linux, Windows, BSD and Solaris. The project has been in active development for over 30 years now, and powers many of the applications you use on a daily basis.

Amazon DynamoDB is a key-value and document database that delivers single-digit millisecond performance at any scale. The database is fully managed, multiregion, multimaster, and durable with built-in security, backup and restore, and in-memory caching for enterprise-scale applications. Amazon DynamoDB is part of Amazon Web Services and integrates well with other cloud-based AWS products.

MongoDB is an open-source document-oriented distributed database built for modern applications. MongoDB uses JSON-like documents with optional schemas and is classified as a NoSQL database. The database is freely distributed under the Server Side Public License, but MongoDB provides commercial version of the database for enterprise-scale applications.

ArangoDB is a database system that was designed to support key/value, document, and graph data to be stored together, and queried via a unified language called AQL. The project is developed by ArangoDB GmbH, and released free and open-source under the Apache License 2.0. The universal "native multi-level" design of the database allows for a flexible approach when structuring and building an application, a feature that many have come to love.

OrientDB is an open-source NoSQL database management system written in Java. The multi-model database supports graph, document, key/value, and object models, where relationships are managed as in graph databases with direct connections between records. The database is extremly efficient and can store over 220,000 records per second on common hardware, and traverse thousands of records in milisecons. OrientDB scales well on multiple machines, thanks to the multi-master replication where there is no single bottleneck on writes like with master-slave replication.