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 (
    74429, 76840, 76841, 77301, 77300, 77302, 
    81947, 81948, 81949, 81987, 81988, 
    81989, 81990, 83173, 83174, 83175, 
    83176, 86389, 86388, 86390, 86408, 
    86409, 86575, 86576, 87281, 87630, 
    87629, 87628, 87627, 87282
  )

Query time 0.00646

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": 30,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (74429,76840,76841,77301,77300,77302,81947,81948,81949,81987,81988,81989,81990,83173,83174,83175,83176,86389,86388,86390,86408,86409,86575,86576,87281,87630,87629,87628,87627,87282)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}