What can be used to build "chains of friends" besides mongodb?

Question

MongoDB

I took habrahabr.ru/blogs/nosql/88246/ as a basis and slowly began to make my own implementation using mongodb. But recently I learned from habrahabr.ru/qa/4735/ that mongodb can “eat up” all the memory on the server and not give it away and is not sharpened at all for use on one server (I confess, as usual, I didn’t read the documentation well). What can be used on a small project (18000 users, 250 online at the peak)?.. It is desirable that the db had an extension for php.

Answer 1

Take the second vps. No need to reinvent the wheel. The cost of VPS for 500 MB is now around 15 bucks per month.

Answer 2

Hehe, it's so flattering that someone refers to you :3
Tell us what kind of project. It’s just that after almost a year on noSQL, I realized that there really are projects where it’s easier to store in tables, and there are where it’s better to store documents.
And in terms of speed, there are leaders here and there, it remains only to choose.

Answer 3

I myself asked a similar question for the same reasons habrahabr.ru/qa/4748/
In short, CouchDB is almost unanimous - now I'm sitting and dealing with it

Answer 4

Neo4j