SELECT 
  cscart_pages.*, 
  cscart_page_descriptions.*, 
  cscart_seo_names.name as seo_name, 
  cscart_seo_names.path as seo_path 
FROM 
  cscart_pages 
  INNER JOIN cscart_page_descriptions ON cscart_pages.page_id = cscart_page_descriptions.page_id 
  LEFT JOIN cscart_seo_names ON cscart_seo_names.object_id = cscart_pages.page_id 
  AND cscart_seo_names.type = 'a' 
  AND cscart_seo_names.dispatch = '' 
  AND cscart_seo_names.lang_code = 'en' 
WHERE 
  cscart_pages.page_id = 50 
  AND cscart_page_descriptions.lang_code = 'en' 
  AND (
    cscart_pages.usergroup_ids = '' 
    OR FIND_IN_SET(0, cscart_pages.usergroup_ids) 
    OR FIND_IN_SET(1, cscart_pages.usergroup_ids)
  ) 
  AND cscart_pages.page_type IN ('T', 'L', 'B', 'F')

Query time 0.00046

JSON explain

{
  "query_block": {
    "select_id": 1,
    "const_condition": "1",
    "table": {
      "table_name": "cscart_pages",
      "access_type": "const",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["page_id"],
      "ref": ["const"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "cscart_page_descriptions",
      "access_type": "const",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["page_id", "lang_code"],
      "ref": ["const", "const"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "cscart_seo_names",
      "access_type": "ref",
      "possible_keys": ["PRIMARY", "dispatch"],
      "key": "PRIMARY",
      "key_length": "206",
      "used_key_parts": ["object_id", "type", "dispatch", "lang_code"],
      "ref": ["const", "const", "const", "const"],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "trigcond(cscart_seo_names.`type` = 'a' and cscart_seo_names.dispatch = '' and cscart_seo_names.lang_code = 'en')"
    }
  }
}