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 = 'en' 
WHERE 
  pfv.variant_id IN (
    1199, 1495, 8210, 1498, 37921, 37925, 
    1515, 1368, 1193, 1201, 1195, 1194, 
    1516, 59499, 1494, 1198, 59761, 1525, 
    1518, 1200, 38109, 1197, 1523, 1524, 
    7431, 1517, 7721, 1493, 38111
  )

Query time 0.00071

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "75.44"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "pfvd",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id",
            "lang_code"
          ],
          "key_length": "9",
          "rows_examined_per_scan": 29,
          "rows_produced_per_join": 29,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "34.84",
            "eval_cost": "5.80",
            "prefix_cost": "40.64",
            "data_read_per_join": "130K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ],
          "attached_condition": "((`webmarco`.`pfvd`.`variant_id` in (1199,1495,8210,1498,37921,37925,1515,1368,1193,1201,1195,1194,1516,59499,1494,1198,59761,1525,1518,1200,38109,1197,1523,1524,7431,1517,7721,1493,38111)) and (`webmarco`.`pfvd`.`lang_code` = 'en'))"
        }
      },
      {
        "table": {
          "table_name": "pfv",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id"
          ],
          "key_length": "3",
          "ref": [
            "webmarco.pfvd.variant_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 29,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "29.00",
            "eval_cost": "5.80",
            "prefix_cost": "75.44",
            "data_read_per_join": "33K"
          },
          "used_columns": [
            "variant_id",
            "position"
          ]
        }
      }
    ]
  }
}