Cannot see today's data in the first half of the day (!?)

Elastic Stack
1

Hello there,
I'm trying to do a request which is depending on a date field

"@timestamp": { "type": "date" }

The query looks like this:

{
  "aggs": {
    "2": {
      "date_histogram": {
        "field": "@timestamp",
        "interval": "3600000ms",
        "time_zone": "Europe/Berlin",
        "min_doc_count": 1
      },
      "aggs": {
        "by_channel": {
          "terms": {
            "field": "cid"
          }
        }
      }
    }
  },
  "size": 0,
  "query": {
    "bool": {
      "must": [
        {
          "match_phrase": {
            "tenant": {
              "query": "My tenant"
            }
          }
        },
        {
          "range": {
            "@timestamp": {
              "gte": 1591567200000,
              "lte": 1591740000000,
              "format": "epoch_millis"
            }
          }
        }
      ]
    }
  }
}

, where "gte": 1591567200000 and "lte": 1591740000000 are 09.06.2020 00:00 and 10.06.2020 00:00.

The problem is that even when I see new data in Discover section of Kibana - it is not returned by this query until middle of a day! Like there is some buffer for new records, or like that. And starting from ~15:00 - it works. And also works for any other day in the past. What is the reason for such a strange behaviour? And how to get the most recent records?

2