Another cool project is bam[1], a constant key/value server built on similar principles. A single input file (in this case, a TSV file instead of the SPL log file) and an index file. The cool thing about bam is that it uses the CMPH[2] library to generate a minimal perfect hash function over the keys in the input file before putting them in the index file.
[1]: https://github.com/StefanKarpinski/bam [2]: http://cmph.sourceforge.net/