Many blockchain systems use LevelDB under the hood to persist their state. For Ebakus, in order to meet the performance requirements and have a DB that is actually aware of the blockchain requirements, I developed a new database: EbakusDB.
This is going to be released as open source software in the next couple of weeks at my github account so keep in touch.
Below is a quick benchmark I did against LevelDB, using LevelDB benchmarks. EbakusDB is multiple times faster in all kinds of operations:
On top of that EbakusDB not only works with key/values but can support schemas and multi indexed tables. And the best feature of all, cheap snapshots. Something like git's cheap branches... Stay tuned ;)