I currently use MySQL and Sphinx to manage a pretty basic database containing nearly 350,000,000 records. It is expected to hit a billion records in less than 200 days (anywhere from 2000 to 5000 records per minute). MySQL is dreadfully slow and Sphinx improves the speed quite a bit, but delta indexing is a pain and I'm not sure if RT indicies are an option.
The data consists of several integer values and one float value. We search through the database based on integer matches and integer ranges (like match maybe 4 integer columns exactly, and we'll give another integer column a range between
Ideally, the best software would be free (in both freedom and free-beer), easy to configure, and returns searches quickly (<0.5 seconds). It should also have libraries available for NodeJS or any other scripting language (not really required).