When querying a Redis database with FT.AGGREGATE, Redis uses the Cursor API to retrieve data from the shards. This may also cause the _FT.CURSOR command may appear in the slow log. The cursor stores the state of the response on the server. It means that the size of the cursor is proportional to the size of the query matches. The best practice is to keep the cursor alive for a short amount of time setting the desired MAXIDLE since it could be expensive, resource-wise.

The default idle timeout is 300000 milliseconds (or 300 seconds), which means that if no activity occurs on the cursor before the idle timeout, the cursor is deleted.

References

Refer to the documentation to learn more about the Cursor API.