Couchbase N1QL SELECT query using ORDER BY is very slow

The following query is very slow:

select meta(d).id, timestamp_utc, d.headline, d.text from data_01 d where type="news" and topic="some_news" and timestamp_utc is not null order by timestamp_utc asc limit 1;

I created the following indices / indexes:

 CREATE INDEX `idx_timestamp_utc` ON `data_01`((-str_to_millis(`timestamp_utc`))) CREATE INDEX `idx_timestamp_utc_some_news` ON `data_01`(`timestamp_utc`) WHERE ((`type` = "news") and (`topic` = "some_news")) CREATE INDEX `idx_topic_and_timestamp_utc` ON `data_01`(`topic`,(-str_to_millis(`timestamp_utc`))) CREATE INDEX `idx_type_news_topic_some_news_timestamp_utc` ON `data_01`((-`timestamp_utc`)) WHERE ((`type` = "news") and (`topic` = "some_news"))

• None of this gives me a better performance than 1 minute.
• There are 3million documents in the bucket topic="some_news" has 300kdocs.
• type="news" has around 2 million docs.
• field timestamp_utc has this format: "2017-01-01T00:00:00+00:00".
• field headline has an average length of ~100 characters.
• field text has an average of length ~2000 characters.

I found similar problems but non of the given fixes and suggestions do work.

Thank you for a response to solve this issue!

I'm running Couchbase 4.5.1 Enterprise Edition (build-2844)