Couchbase Mobile supports a JSON document style NoSQL data model that accommodates both standard JSON data types and binary data, such as images and PDFs, through attachments or blobs. These attachments can be synced between Couchbase Lite clients and the server using the Sync Gateway. The article explores the creation, retrieval, and update of binary data attachments in Couchbase Mobile 2.x deployments, detailing the differences in handling attachments between versions 1.x and 2.x. Developers are guided on how to manage these discrepancies, especially when dealing with the Sync Gateway's backward compatibility with the 1.x style attachments. The post also discusses the limitations on attachment size and quantity, the robustness of the sync protocol in handling failures, and best practices for managing large binary data, such as storing them externally and using references. Additionally, the article touches on current limitations with Couchbase Server SDKs for direct attachment management and hints at future improvements.