DocumentDB claims to be compatible with MongoDB, but its compatibility is inconsistent and limited. DocumentDB lacks many features that come standard in MongoDB, such as native sharding, scaling writes, and replicate and scale beyond a single region. It also has limitations on failover time, retryable writes, integrated text search, geospatial processing, hedged reads, online archiving, and client-side field-level encryption. In contrast, MongoDB offers more flexibility in terms of scalability, data distribution, and security features. DocumentDB also lacks rich data types like decimal data types, which can be critical for financial and scientific applications. Additionally, DocumentDB does not offer platform agility, allowing users to move between different platforms with ease.