SELECT 
  pfv.variant_id, 
  pfv.position, 
  pfvd.variant 
FROM 
  cscart_product_feature_variants AS pfv 
  INNER JOIN cscart_product_feature_variant_descriptions AS pfvd ON pfv.variant_id = pfvd.variant_id 
  AND pfvd.lang_code = 'ru' 
WHERE 
  pfv.variant_id IN (
    1373, 1357, 1358, 1381, 1393, 1374, 6, 
    1371, 1365, 1375, 1385, 1380, 1359, 
    1360, 1361, 1362, 1363, 1364, 1366, 
    1367, 1368, 1369, 1370, 1376, 1379, 
    1377, 1382, 1383, 1384, 1386
  )

Query time 0.00056

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "31.51"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id"
          ],
          "key_length": "3",
          "rows_examined_per_scan": 30,
          "rows_produced_per_join": 30,
          "filtered": "100.00",
          "index_condition": "(`test_uchur_k`.`pfv`.`variant_id` in (1373,1357,1358,1381,1393,1374,6,1371,1365,1375,1385,1380,1359,1360,1361,1362,1363,1364,1366,1367,1368,1369,1370,1376,1379,1377,1382,1383,1384,1386))",
          "cost_info": {
            "read_cost": "18.01",
            "eval_cost": "3.00",
            "prefix_cost": "21.01",
            "data_read_per_join": "46K"
          },
          "used_columns": [
            "variant_id",
            "position"
          ]
        }
      },
      {
        "table": {
          "table_name": "pfvd",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id",
            "lang_code"
          ],
          "key_length": "9",
          "ref": [
            "test_uchur_k.pfv.variant_id",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 30,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "7.50",
            "eval_cost": "3.00",
            "prefix_cost": "31.51",
            "data_read_per_join": "93K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}