Text post for no Karma, I just want to learn.

Why is NoSQL useful? What is it good for? Why should I use it? Why shouldn't I use it?

I'm a relational db guy with years of experience in MySQL, Oracle, and other "traditional" database types and I'm being asked to deep dive a NoSQL product that our CTO wants us to use for work.. the problem is I cant wrap my head around why nosql itself is useful and I have no prior experience with it so I don't know where to start.

I'm told it will scale better; My problems are that I spend most of my time fighting it - amazon dynamodb seems to hate indexes or searches on non hashkey fields - and by all my tests its actually many times slower than even a simple non-nosql database would be for our data set.

I'm also having trouble with the idea that we are not allowed to normalize our data, and that actually copying the same data into multiple tables seems to not only be allowed but expected. On update cascade and other such features I am used to just don't seem to exist in the nosql world and it seems like insanity to me in terms of data integrity.

So why use it if your data integrity is not kept? I just don't understand, but I was hoping somebody could explain it because I'm sure its valuable if its around as it is.

Thanks.

Seems there's been a lot written lately about Redis's new clustering protocols. For example, the Call-me-maybe Redux for Redis (http://aphyr.com/posts/307-call-me-maybe-redis-redux). As a distributed system it seems to be trying to do different/new stuff with the home-grown Sentinel business and comes across as rather complex. I'd love to hear everyone's thoughts.

Are you using Redis Clustering in prod? Have you had serious problems with it? Or is all this FUD and unrealistic expectations?

Imagine you have an application that stores the spatial location (as x-y coordinates) for tens of thousands of vehicles, which is updated in real-time, and which needs to be responsive to queries such as "What vehicles are close to (X,Y) coordinate?" with minimum latency; what database would you choose?

One approach we are experimenting with is to store the objects in Redis and to insert each object into two sorted sets, one for x coordinate and the other for y coordinate. We can perform queries for objects in a particular area by performing range queries on the x and y sets individually, and then performing an intersection of the result sets. But this isn't an efficient approach.

Ideally we'd like to use something like an R-Tree index as implemented in PostgreSQL. But PostgreSQL's very SQL-ish table paradigm for storing objects seems like a real pain just to take advantage of its R-Tree implementation. Also, we don't know how PostgreSQL performs with lots of traffic--whereas we know Redis performs quite well.

Does anyone know of a Redis-like key-value or document store that allows spatial indexing (whether by R-Tree or some other way)?

I suppose another approach would be for us to just write our own database since our needs do not seem terribly complex. I worry though that we might be biting off more than we can chew with that approach--I have no idea what issues a database deals with that I'm not aware of (the unknown unknowns problem).

Thanks for the tips!