SELECT 
  * 
FROM 
  cscart_ab__sr_reviews_pages AS rp 
  LEFT JOIN cscart_ab__sr_reviews_page_descriptions AS rpd ON rp.reviews_page_id = rpd.reviews_page_id 
  AND rpd.lang_code = 'ru' 
WHERE 
  object_id = 313 
  AND object_type = 'category'

Query time 0.00015

JSON explain

{
  "query_block": {
    "select_id": 1,
    "const_condition": "1",
    "table": {
      "table_name": "rp",
      "access_type": "const",
      "possible_keys": ["object_id"],
      "key": "object_id",
      "key_length": "102",
      "used_key_parts": ["object_id", "object_type"],
      "ref": ["const", "const"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "rpd",
      "access_type": "const",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "10",
      "used_key_parts": ["reviews_page_id", "lang_code"],
      "ref": ["const", "const"],
      "rows": 1,
      "filtered": 100
    }
  }
}