Key-value store, B+tree. Lightning fast reads, unmatched by anything.
Lightning fast bulk loads.
Memory-mapped files for persistent storage with all the speed of an in-memory
database. No tuning configuration required. Full ACID transaction support.
MVCC, readers run lockless. Tiny code, written in C, compiles to under 32KB of
x86-64 object code. Modeled after the BerkeleyDB API for easy migration from
Berkeley-based code. Benchmarks against LevelDB, Kyoto Cabinet, SQLite3, and
BerkeleyDB are available, plus full paper and presentation slides.
I'm also doing a new presentation on MDB at LinuxCon in San Diego this August 29.