etcd-io/bbolt is a repository that provides an embedded key-value database for Go applications. Embedded means opening the database directly inside the program instead of running it as a separate server, and a key-value database is a structure that stores values one by one, pairing each one with a key used as its name. It is a fork of Ben Johnson's Bolt, and the latest public release is v1.5.0.
The language is Go, the license is MIT, and it is recorded as having 9786 stars; the repository was created on 2017-06-17. The MIT license is a form where the conditions for use, modification, and redistribution are briefly summarized. The README states that bbolt maintains backward compatibility with the Bolt API while fixing bugs and improving performance, and that it also provides features that Bolt did not have. This fork aims to carry on the ongoing maintenance and development of Bolt in order to increase reliability and stability. The explanation that it maintains API backward compatibility gives those who are considering moving over code written for Bolt a reason to review it.
However, what exactly changed in v1.5.0 can only be known by checking the repository's release notes directly, and no figures comparing performance are given. How far the performance improvements mentioned in the README actually reach is difficult to judge at this point. So for now, this repository can only be pointed out as a candidate for applications where the embedded approach is a good fit.