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 (
    70578, 70577, 70579, 70659, 70658, 70657, 
    70656, 70655, 73131, 73130, 73129, 
    73132, 76058, 76057, 76911, 76912, 
    78488, 80882, 80883, 81493, 81494, 
    81733, 81734, 81737, 81738, 82399, 
    82400, 82401, 84766, 84292, 84293, 
    84418, 84419, 84420, 84421, 85973, 
    85974, 85975, 85976, 85977, 85978, 
    85979
  )

Query time 0.00185

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": 42,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (70578,70577,70579,70659,70658,70657,70656,70655,73131,73130,73129,73132,76058,76057,76911,76912,78488,80882,80883,81493,81494,81733,81734,81737,81738,82399,82400,82401,84766,84292,84293,84418,84419,84420,84421,85973,85974,85975,85976,85977,85978,85979)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}