LevelDB is an open-source key-value storage library developed by Google. It is designed for fast read and write operations, making it suitable for applications that require efficient data storage and retrieval. LevelDB stores data in a sorted order, allowing for quick access to values based on their keys. The library uses a log-structured merge-tree (LSM tree) structure, which helps optimize write performance by batching updates. LevelDB is often used in various applications, including databases and caching systems, due to its simplicity and effectiveness in handling large amounts of data.