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 (
    71065, 71066, 71075, 71076, 73980, 73979, 
    73978, 73981, 74876, 74875, 74874, 
    74877, 75641, 75642, 75643, 79217, 
    79218, 79219, 79256, 79255, 79260, 
    79266, 79265, 79275, 79281, 79285, 
    79286, 79296, 79295, 81601, 81610, 
    81611, 81612, 81613, 81614, 81615, 
    81616, 81617, 81602, 81603, 81604, 
    81605, 81606, 81607, 81608, 81609, 
    85275, 85276, 85277, 85278, 85279, 
    87216, 87215, 87214, 80109, 80108
  )

Query time 0.00500

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 (71065,71066,71075,71076,73980,73979,73978,73981,74876,74875,74874,74877,75641,75642,75643,79217,79218,79219,79256,79255,79260,79266,79265,79275,79281,79285,79286,79296,79295,81601,81610,81611,81612,81613,81614,81615,81616,81617,81602,81603,81604,81605,81606,81607,81608,81609,85275,85276,85277,85278,85279,87216,87215,87214,80109,80108)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}