Fast queries in batches

[magorbe]

Hi. I'm doing a search on ES and it's:

query = {
            "_source": false,                                      
            "query": {
                "ids": {

                    "values": ids
                }
            }
        }

I do it in batches of 100 ids. And the response times I get are the following:

78it [00:00, 777.80it / s]
102it [00:02, 34.64it / s]
200it [00:04, 37.07it / s]
300it [00:06, 38.28it / s]
400it [00:09, 38.45it / s]
500it [00:11, 39.17it / s]
600it [00:14, 39.93it / s]
700it [00:16, 41.03it / s]
800it [00:18, 41.58it / s]
900it [00:27, 23.02it / s]
1000it [00:36, 17.41it / s]
1100it [00:45, 14.95it/s]
1200it [00:55, 12.95it/s]
1300it [01:05, 11.87it/s]
1400it [01:15, 11.42it/s]
1500it [01:24, 11.26it/s]

Does anyone know why this decrease in speed as the consultations progress? Is there any way to maintain the initial speed?

Thanks!