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 (
    71549, 71680, 71681, 72427, 72428, 73140, 
    73139, 73138, 73585, 73584, 75523, 
    75524, 76827, 77696, 77695, 77697, 
    78992, 78993, 79229, 79231, 79230, 
    79349, 79350, 79351, 81479, 81480, 
    81505, 81506, 81507, 81508, 81676, 
    83392, 83399, 83400, 83401, 83402, 
    83403, 83404, 83405, 83393, 83394, 
    83395, 83396, 83397, 83398, 84386, 
    84387, 84388, 84389, 84390, 85226, 
    86449, 86448, 86447, 86446, 86445, 
    86444, 86453, 86452, 86443, 86451, 
    86450, 87892, 87893
  )

Query time 0.00442

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": 64,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (71549,71680,71681,72427,72428,73140,73139,73138,73585,73584,75523,75524,76827,77696,77695,77697,78992,78993,79229,79231,79230,79349,79350,79351,81479,81480,81505,81506,81507,81508,81676,83392,83399,83400,83401,83402,83403,83404,83405,83393,83394,83395,83396,83397,83398,84386,84387,84388,84389,84390,85226,86449,86448,86447,86446,86445,86444,86453,86452,86443,86451,86450,87892,87893)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}