Hi @Y2DTL ,

Here's an answer from documentation: 

A stream-static join joins the latest valid version of a Delta table (the static data) to a data stream using a stateless join.

When Databricks processes a micro-batch of data in a stream-static join, the latest valid version of data from the static Delta table joins with the records present in the current micro-batch. Because the join is stateless, you do not need to configure watermarking and can process results with low latency. The data in the static Delta table used in the join should be slowly-changing.

https://docs.databricks.com/gcp/en/transform/join#stream-static-joins