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 (
    71488, 71487, 71489, 71494, 71495, 71496, 
    71497, 74435, 74436, 78424, 78423, 
    78425, 78422, 79217, 79218, 79219, 
    79226, 79227, 79228, 79248, 79249, 
    79250, 82381, 82382, 84325, 84326, 
    84327, 84328, 84413, 84414, 84415, 
    84416, 84417, 85989, 85988, 85987, 
    85986, 85985, 85984, 86598, 86599
  )

Query time 0.00819

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": 41,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (71488,71487,71489,71494,71495,71496,71497,74435,74436,78424,78423,78425,78422,79217,79218,79219,79226,79227,79228,79248,79249,79250,82381,82382,84325,84326,84327,84328,84413,84414,84415,84416,84417,85989,85988,85987,85986,85985,85984,86598,86599)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}