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 (
    68250, 68249, 68248, 68247, 68246, 68251, 
    68882, 68883, 69903, 69902, 69904, 
    70373, 70374, 70372, 71565, 71566, 
    71578, 71576, 71577, 73414, 73415, 
    73413, 73448, 73447, 73446, 74243, 
    74242, 74241, 74244, 74259, 74258, 
    74257, 74260, 74795, 75769, 75767, 
    75768, 75770, 78288, 78289, 78331, 
    78332, 79034, 79035, 81033, 81032, 
    81034, 82422, 82425, 82424, 82423, 
    85607, 85608, 85609, 83856, 83855
  )

Query time 0.00647

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": 56,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (68250,68249,68248,68247,68246,68251,68882,68883,69903,69902,69904,70373,70374,70372,71565,71566,71578,71576,71577,73414,73415,73413,73448,73447,73446,74243,74242,74241,74244,74259,74258,74257,74260,74795,75769,75767,75768,75770,78288,78289,78331,78332,79034,79035,81033,81032,81034,82422,82425,82424,82423,85607,85608,85609,83856,83855)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}