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 (
    75765, 75763, 75764, 75766, 75777, 75780, 
    75778, 75779, 75808, 75805, 75806, 
    75807, 75812, 75809, 75810, 75811, 
    81325, 81332, 81328, 81333, 81327, 
    81326, 81329, 81330, 81331, 87232, 
    87233
  )

Query time 0.00129

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": 27,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (75765,75763,75764,75766,75777,75780,75778,75779,75808,75805,75806,75807,75812,75809,75810,75811,81325,81332,81328,81333,81327,81326,81329,81330,81331,87232,87233)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}