MongoDB vs. Redis vs. Cassandra for a fast-write, temporary row storage solution

Question

I\'m building a system that tracks and verifies ad impressions and clicks. This means that there are a lot of insert commands (about 90/second average, peaking at 250) and some

Answer 1

All three solutions (four if you count flat-files) will give you blazing fast writes. The non-relational (nosql) solutions will give you tunable fault-tolerance as well for the purposes of disaster recovery.

In terms of scale, our test environment, with only three MongoDB nodes, can handle 2-3k mixed transactions per second. At 8 nodes, we can handle 12k-15k mixed transactions per second. Cassandra can scale even higher. 250 reads is (or should be) no problem.

The more important question is, what do you want to do with this data? Operational reporting? Time-series analysis? Ad-hoc pattern analysis? real-time reporting?

MongoDB is a good option if you want the ability to do ad-hoc analysis based on multiple attributes within a collection. You can put up to 40 indexes on a collection, though the indexes will be stored in-memory, so watch for size. But the result is a flexible analytical solution.

Cassandra is a key-value store. You define a static column or set of columns that will act as your primary index right up front. All queries run against Cassandra should be tuned to this index. You can put a secondary on it, but that's about as far as it goes. You can, of course, use MapReduce to scan the store for non-key attribution, but it will be just that: a serial scan through the store. Cassandra also doesn't have the notion of "like" or regex operations on the server nodes. If you want to find all customers where the first name starts with "Alex", you'll have to scan through the entire collection, pull the first name out for each entry and run it through a client-side regex.

I'm not familiar enough with Redis to speak intelligently about it. Sorry.

If you are evaluating non-relational platforms, you might also want to consider CouchDB and Riak.

Hope this helps.