I would have to agree. Stackoverflow is in the alexa top 100, with over 400 million page views per month, and it runs off a single MS SQL Server instance (with a hot replica), with a Redis cache in front of it.

All the high-scale users of nosql systems end up having to learn a lot of arcane technical wizardry to make it scale (as demonstrated by the slidedeck linked here), and I'm not convinced it's actually easier to scale something like mongo than a traditional RDBMS.

No , there is something specific to MongoDB. Some NoSQL dbs are fine for some purposes ( multi-master sync for couchdb ,graphs for Neo4j ... )

MongoDB problem is that it promises too much and fail to deliver on a lot of levels. You cant expect to do all the operations one can do on a RDBMS on a NoSQL database and still scale horizontally,while maintaining data integrity. A good NoSQL db should have little features , but features that work very well. I like CouchDB for instance i use it in my apps to store customer infos that need to be synced accross multiple device, but i would NOT build an ecommerce app with it only...

NoSQL dbs solves specific problems. It does not solve the problems relational databases are for.

So selling MongoDB as a replacement for PostGreSQL or Mysql is a blatant lie.It will not work.

You are pretty violent against MongoDB. Any reason why?

I suspect the reason that Mongo attracts so much hate is that it's more heavily marketed/evangelised than other NoSQL DBs - so more in the public eye and people expect more from it. Since the reality is that Mongo is not yet a technically strong product (regardless of its merits in terms of ease of use and getting simple things done quickly), it's bound to attract more negative attention.

Bingo. My brief experience with Mongo a few years ago was in a situation where it got selected in order to use something "new and cool". My job was to produce some reports from the data. Guess what reports require? Joins. The whole mess was slow and sucked, and the client belatedly realized that MongoDB was a shitty choice for what they needed, which could have been handled by Postgres without breaking a sweat.

Having spent the last two years trying to make MongoDB work at large scale and only succeeding because I have a ton of resources (200+ db hosts), I can say it's more than just the spotlight.

It is a fundamentally broken product.

Fair enough - I have no direct personal experience with Mongo myself. Coming from a more traditional DB background, what I've read indicates it has a lot of technological flaws, but I didn't want to be too harsh in my judgement without personal experience.

For my own curiosity, what issues caused you the most trouble? The lack of transactions combined with the extremely coarse grained write locking were what put me off the most.

Read performance compared to a lot of other offerings is a significant issue.

However, one of the biggest issue is the entire sharding design that is incredibly delicate and wouldn't pass even the most basic high availability requirements. I could go into a lot of detail about why it's bad but it would take too long.

After that, it's the hardcoded limitations that prevent true multi-datacentre sharding, the previously mentioned CPU issues with mongos, broken replica selection, inability to control primary/replica setting manually, etc.

The list is virtually endless.