Sync-in has been used in production for several years by multiple companies of various sizes. As mentioned in the design documentation, the solution can support millions of files — and very likely more, since the main limitation comes from the underlying file system. The real bottleneck is therefore related to storage performance (IO, latency, throughput, etc.).

Regarding collaboration, Sync-in relies on a system of exclusive and shared locks depending on the use case. In document collaboration mode, a shared lock is used to allow simultaneous editing. For other operations (uploads, structural modifications, etc.), exclusive locks are applied to prevent collisions.