> by the time you hit the point where you need a NoSQL solution to handle scaling issues
See, people keep saying that NoSQL databases give you a performance boost over traditional relational solutions (MySQL and Postgres), but exactly where does this performance boost come from? I can understand the appeal of in-memory databases or using caching (Memcached) to supplement the relational solution, but it seems like the vast majority of Mongo's performance benefits come from eschewing ACID guarantees rather than document databases being inherently faster.
Imgur is set up to have almost the same structure and features as reddit. Users have images, there are sections duplicating the subreddit structure, images have comments, comments have votes and voters. That's a lot of related info that isn't strictly hierarchal, and I believe you'd run into the same problem described in the article - the need to manually do joins and associate types of data in your application code to ensure consistency and lack of duplication.
Re:Why You Should Never Use MongoDB
by liveoneggs on Monday November 11, 2013 @01:13PM
(#6712984)
except there are relationships in imgur. For example when it groups images from different subreddits or creates albums.
That said, even if somebody was building something like Imgur, I would still advise that the start with a SQL database. SQL is very well-understood, and you will have no problem finding developers that have deep experience in your SQL engine of choice.
More importantly, by the time you hit the point where you need a NoSQL solution to handle scaling issues, you will have achieved product-market fit, and can make a sane technology decision based on your vastly greater understanding of the business needs.