Collection-scoped MongoDB change streams

MongoDB pipelines can now opt into collectionScopedMode for tighter isolation between collections. Artie opens an independent stream for each configured collection, polls streams round-robin, and stores a separate resume token for each one. Ordering is preserved within a collection, not across collections. The database-level stream remains the default; this mode requires sufficient maxConcurrentStreams capacity and a maxPoolSize greater than the number of active streams.

Why this matters

• Let a busy collection resume independently after a failure without affecting its neighbors
• Get per-collection ordering and recovery guarantees that a shared CDC stream cannot offer