Couchbase n1ql pagination so slow

[vsr1]

CREATE INDEX ix1 ON messages(DISTINCT displayTo, threadId, createdDate DESC);

SELECT RAW m.threadId
FROM messages AS m
WHERE ANY v IN m.displayTo SATISFIES v = 10 END
GROUP BY m.threadId
LETTING  od = MAX(m.createdDate)
ORDER BY od DESC
OFFSET 0 
LIMIT 20;