
Ask HN: How does Twitter implement following and followers between users? - benkovy
I have always been curious as to how twitter implemented this in their user model. How do they keep track of who the user is following and who is following the user?
======
tedmiston
In 2010, Twitter was using a graph database, FlockDB, instead of a relational
database to implement their social graph where relationships like following
and followers are represented as edges between nodes that represent people.
It's since been deprecated, and I'm not sure what type of database they're
using today. Anyway, they have a nice write-up blog post [1] and FlockDB is
open source [2].

[1]:
[https://blog.twitter.com/engineering/en_us/a/2010/introducin...](https://blog.twitter.com/engineering/en_us/a/2010/introducing-
flockdb.html)

[2]: [https://github.com/twitter-archive/flockdb](https://github.com/twitter-
archive/flockdb)

------
bsvalley
\--- USER TABLE ---

| USER_ID |

| USERNAME |

| NB_FOLLOWERS |

| TWEETS -> List of TWEET_ID's |

| FOLLOWING -> List of USER_ID's |

| FOLLOWED_BY -> List of USER_ID's |

etc.

NB_FOLLOWERS, FOLLOWING and FOLLOWED_BY are updated when a USER
follows/unfollows another USER.

------
miguelrochefort
User1 follows User2

User1 follows User3

User3 follows User1

User3 follows User5

...

