The solardin.claim_datum_stream_poll_task() database function is used to "claim" a Cloud Datum Stream Poll Task for execution. This function queries the solardin.cin_datum_stream_poll_task table like this:

SELECT *
FROM solardin.cin_datum_stream_poll_task
WHERE status = 'q'
AND exec_at <= CURRENT_TIMESTAMP
LIMIT 1

There is an index already defined that looks like it was meant to be used by that query:

CREATE INDEX cin_datum_stream_poll_task_exec_idx
ON solardin.cin_datum_stream_poll_task
	(exec_at DESC) INCLUDE (status);

However the index is not actually used, when testing with EXPLAIN. In addition, the query does a SELECT * so including the status column alone in the index via the INCLUDE (status) statement is not actually of any benefit there.

For the best query access time, perhaps a different, partial index like the following would be better:

CREATE INDEX cin_datum_stream_poll_task_exec_idx
ON solardin.cin_datum_stream_poll_task
	(exec_at) WHERE (status = 'q');

and then get the index in use by tweaking the claim query to add an ORDER BY exec_at DESC like this:

SELECT *
FROM solardin.cin_datum_stream_poll_task
WHERE status = 'q'
AND exec_at <= CURRENT_TIMESTAMP
ORDER BY exec_at
LIMIT 1