B+-tree has been used as one of the main index structures in database fields for more than four decades. However, with the unprecedented amount of data being generated by modern, global-scale web, mobile, and IoT applications, typical B+-tree implementations are beginning to show scalability and performance issues. Various key-value storage engines with variants of B+-tree such as log-structured merge tree (LSM-tree), have been proposed to address these limitations. At Couchbase, we have been working on a new key-value storage engine, ForestDB, that has a main index structure based on Hierarchical B+- Tree (based Trie or HB+-Trie). and provides high scalability and performance. In this presentation, we introduce ForestDB and discuss why ForestDB is a good fit for modern big data applications.