Would you mind sharing the query? If you're hitting OOM exceptions with a dataset of that size there may be a typo in the query that's doing some sort of traveling salesman operation.

e.g.,

//grabs literally EVERY node in your database

MATCH (Person)-[KNOWS]-(Friend)

//only the people who have a KNOWS relationship between them

MATCH (person:Person)-[:KNOWS]-(Friend:Person)