PostgreSQL Alternatives for Web

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.

HarperDB is a full-featured data management platform that runs from edge to cloud, and anywhere in between. It provides an easy to use REST API, a sleek management studio, quick installation, and limited database configuration, while being language agnostic. With HarperDB you can insert JSON, query with performant SQL including JOINS and full CRUD operations.  Enhanced features like built in Math.js and GeoJSON.

CouchDB is a free and open-source document-oriented NoSQL database developed by the Apache Foundation. The database is written and implemented in the language Erlang and provides the use of multiple formats and protocols to store, transfer, and process data. With CouchDB you query data with JavaScript using MapReduce, and HTTP for an API. Which can be done across multiple distributed CouchDB instances as the database has the ability to synchronize multiple copies of the same database, across servers.

NuoDB is a distributed relational database management system utilizing SQL. The database is architected to meet the rapidly evolving demands of today's enterprises, NuoDB can be used to deploy on-premise, extend to the cloud, scale on demand, eliminate downtime and reduce total cost of ownership. All while maintaining SQL compatibility and a workflow that most developers are familiar with.

GraphDB is a simple graph API for SQL Server. The GraphDB database resides inside of your SQL server and together with .Net 4.5 assemblies partitioned into a client and an admin API. The Client API allow users to connect to a GraphDB store and store graphs of entities in workspaces. The API has a rich set of data-, security- and graph-related methods to easily manage entities, collaboration and networks. While the Admin APU allows you store and manage data, and manage security related tasks and user accounts.