Actually much of this is not true.
* All Neo4j versions have caching
* Neo4j Enterprise is available for free for any AGPL project and for personal use and early startups
* Neo4j is not an in-memory database, it is a persistent, fully transactional database, it uses the available memory for caching the hot dataset
Re:Cayley – An open-source graph database
by atombender on Thursday June 26, 2014 @04:54PM
(#7951530)
> All Neo4j versions have caching
I was actually referring to the "High-Performance Cache" mentioned in the feature matrix.
> Neo4j Enterprise is available for free for any AGPL project
I was really talking about a commercial setting. How many companies deploy a fully open-source project (ie., honouring the requirements of the AGPL) in a redundant data center? Not a lot, I imagine.
> Neo4j is not an in-memory database
True, it seems I was misinformed about that.
It's pretty much useless in a server environment since even replication isn't possible; if you want a redundant setup -- which you will -- you will have to keep the nodes synchronized yourself. Not to mention that since Neo4j is an in-memory database, it puts a hard limit on your dataset size.
They have a "Personal License" [2], but it lasts for one year and you're not allowed to use it if you have capital funding or a certain amount of revenue.
[1] http://neo4j.com/subscriptions/
[2] http://www.neotechnology.com/terms/personal_us/