Streams as the Engine Behind Global Tables

DynamoDB Streams isn't only a tool for triggering Lambda functions directly — it's also the underlying mechanism AWS uses to implement Global Tables' cross-Region replication: every write to a table is captured on the stream, and Global Tables' replication process consumes that same stream to propagate the change to every other participating Region. This is why enabling Global Tables automatically enables Streams on the table if it isn't already on. Understanding this connection clarifies two practical points: first, a table that already has Streams enabled and consumed by your own Lambda triggers can become a Global Table without breaking that existing consumer, since Streams supports multiple independent consumers reading the same log. Second, the 24-hour retention window on Streams matters operationally for replication too — if a Region falls offline for longer than that window and Global Tables' internal replication process can't catch up from the stream, a full resync is required rather than an incremental one, which is a meaningful operational consideration for very long Regional outages.