RocksDB Storage Engine: You can now use as much data in ArangoDB as you can fit on your disk. Plus, you can enjoy performance boosts on writes by having only document-level locks
Pregel: We implemented distributed graph processing with Pregel to discover hidden patterns, identify communities and perform in-depth analytics of large graph data sets.
Fault-Tolerant Foxx: The Foxx management internals have been rewritten from the ground up to make sure multi-coordinator cluster setups always keep their services in sync and new coordinators are fully initialized even when all existing coordinators are unavailable.
Enterprise: Working with some of our largest customers, we’ve added further security and scalability features to ArangoDB Enterprise like LDAP integration, Encryption at Rest, and the brand new Satellite Collections.
Also see What's New in 3.2.
SmartGraphs: Scale with graphs to a cluster and stay performant. With SmartGraphs you can use the "smartness" of your application layer to shard your graph efficiently to your machines and let traversals run locally.
Encryption Control: Choose your level of SSL encryption
Auditing: Keep a detailed log of all the important things that happened in ArangoDB.
Also see What's New in 3.1.
self-organizing cluster with synchronous replication, master/master setup, shared nothing architecture, cluster management agency.
Deeply integrated, native AQL graph traversal
VelocyPack as new internal binary storage format as well as for intermediate AQL values.
Persistent indexes via RocksDB suitable for sorting and range queries.
Foxx 3.0: overhauled JS framework for data-centric microservices
Significantly improved Web Interface
Also see What's New in 3.0.