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 = 'vi' 
WHERE 
  pfv.variant_id IN (
    68602, 68603, 69666, 69665, 69667, 71341, 
    71339, 71338, 71337, 71336, 71335, 
    71334, 71333, 71332, 71331, 71342, 
    71626, 71624, 71623, 71622, 71625, 
    74232, 74231, 74230, 74803, 74804, 
    75622, 75623, 75624, 75625, 75626, 
    81705, 81706, 84725, 84724, 82134, 
    82133, 82135, 82657, 82658, 82660, 
    82661, 79169, 86319, 86318, 86317, 
    86316, 86590, 86591, 86594, 86595, 
    87185, 87189, 87188, 87187, 87186, 
    87232, 87233, 84152, 87604, 84154, 
    87603, 87602, 87601, 84156, 84153, 
    78095, 78105, 78094, 78104, 78112, 
    78111, 78110, 78109, 78108, 78107, 
    78106, 78096, 78097, 78098, 78099, 
    78100, 78101, 78102, 78103
  )

Query time 0.01638

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["variant_id"],
          "rows": 85,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (68602,68603,69666,69665,69667,71341,71339,71338,71337,71336,71335,71334,71333,71332,71331,71342,71626,71624,71623,71622,71625,74232,74231,74230,74803,74804,75622,75623,75624,75625,75626,81705,81706,84725,84724,82134,82133,82135,82657,82658,82660,82661,79169,86319,86318,86317,86316,86590,86591,86594,86595,87185,87189,87188,87187,87186,87232,87233,84152,87604,84154,87603,87602,87601,84156,84153,78095,78105,78094,78104,78112,78111,78110,78109,78108,78107,78106,78096,78097,78098,78099,78100,78101,78102,78103)"
        }
      },
      {
        "table": {
          "table_name": "pfvd",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["variant_id", "lang_code"],
          "ref": ["dev_db.pfv.variant_id", "const"],
          "rows": 1,
          "filtered": 100,
          "index_condition": "pfvd.lang_code = 'vi'"
        }
      }
    ]
  }
}