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, 1540, 1541, 
    1554, 1555, 1556, 1206, 1216, 1564, 
    1242, 1550, 1565, 1215, 1213, 1212
  )

Query time 0.00038

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": 25,
      "filtered": 100,
      "index_condition": "pfv.variant_id in (1498,1499,1500,1501,1514,1238,1207,1504,1518,1519,1520,1540,1541,1554,1555,1556,1206,1216,1564,1242,1550,1565,1215,1213,1212)"
    },
    "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'"
    }
  }
}