I recommend this old but gold advent post from 3 years ago: Dec 12th, 2018: [EN][Elasticsearch] Automatically adding a timestamp to documents
It shows how to use a pipeline that adds an ingest timestamp to every document you push. That's the most accurate way you can use and it allows you to lower the value for delay. Note that by default lucene uses a refresh interval of 1s, so you should not set delay to a lower value, but e.g. use 2s. Of course you can tweak this further, but I guess that should already meet recency requirements for most users.