When comparing HarperDB vs ArangoDB, the Slant community recommends ArangoDB for most people. In the question“What are the best NoSQL databases to use for Node.js applications?” ArangoDB is ranked 6th while HarperDB is ranked 7th. The most important reason people chose ArangoDB is:
You can model your data as documents or as a graph - no data model lock-in. You can even combine both models and use them in a single AQL query.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Document and graph-orientend
You can model your data as documents or as a graph - no data model lock-in. You can even combine both models and use them in a single AQL query.
Pro Supports joins
Unlike many NoSQL databases, ArangoDB does support joins in AQL queries.
Pro JavaScript-API
You can extend ArangoDB using JavaScript that runs directly on the Server (Google V8). You can build data-centric microservices that aggregate, validate, transform or enrich data (It's up to you, plain JavaScript) and provide those via a custom API route.
Pro Transaction save
You can use ACID Transactions for short and small data retrieval and/or modification operations in ArangoDB.
Pro Easy cluster setup
Pro Powerful Java Driver (Sync & Async)
ArangoDB has a very good Java Driver for synchronous and asynchronous. In addition the team there is working on a Spring Data integration.