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 (
    1498, 1499, 1500, 1501, 1514, 1238, 1207, 
    1504, 1518, 1519, 1520, 1521, 1522, 
    1523, 1540, 1541, 1552, 1600, 1554, 
    1555, 1558, 1559, 1561, 1560, 1556, 
    1205, 1206, 1216, 1564, 1242, 1550, 
    1565, 1239, 1566, 1567, 1208, 1218, 
    1577, 1578, 1579, 1580, 1581, 1582, 
    1583, 1584, 1586, 1587, 1215, 1213, 
    1212
  )

Query time 0.00087

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "pfv",
      "access_type": "range",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["variant_id"],
      "rows": 50,
      "filtered": 100,
      "index_condition": "pfv.variant_id in (1498,1499,1500,1501,1514,1238,1207,1504,1518,1519,1520,1521,1522,1523,1540,1541,1552,1600,1554,1555,1558,1559,1561,1560,1556,1205,1206,1216,1564,1242,1550,1565,1239,1566,1567,1208,1218,1577,1578,1579,1580,1581,1582,1583,1584,1586,1587,1215,1213,1212)"
    },
    "table": {
      "table_name": "pfvd",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["variant_id", "lang_code"],
      "ref": ["ymonline_livedata.pfv.variant_id", "const"],
      "rows": 1,
      "filtered": 100,
      "index_condition": "pfvd.lang_code = 'en'"
    }
  }
}