SELECT 
  * 
FROM 
  cscart_sg_user_activity_log 
WHERE 
  user_id = 0 
  AND session_id = '' 
  AND lang_code = 'en' 
ORDER BY 
  timestamp DESC 
LIMIT 
  50

Query time 0.01951

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 8.9750922,
    "nested_loop": [
      {
        "read_sorted_file": {
          "filesort": {
            "sort_key": "cscart_sg_user_activity_log.`timestamp` desc",
            "table": {
              "table_name": "cscart_sg_user_activity_log",
              "access_type": "ALL",
              "loops": 1,
              "rows": 53485,
              "cost": 8.9750922,
              "filtered": 100,
              "attached_condition": "cscart_sg_user_activity_log.user_id = 0 and cscart_sg_user_activity_log.session_id = '' and cscart_sg_user_activity_log.lang_code = 'en'"
            }
          }
        }
      }
    ]
  }
}

Result

id user_id session_id action item_id category_id search_query timestamp lang_code
54763 0 view 459017 0 1782691772 en
54762 0 view 447289 0 1782691767 en
54761 0 view 411798 0 1782691762 en
54760 0 cat_view 0 305 1782691757 en
54759 0 cat_view 0 305 1782691752 en
54757 0 cat_view 0 287 1782685985 en
54755 0 cat_view 0 305 1782685798 en
54754 0 cat_view 0 305 1782685793 en
54752 0 cat_view 0 305 1782685783 en
54749 0 cat_view 0 305 1782685768 en
54746 0 cat_view 0 305 1782685752 en
54745 0 cat_view 0 305 1782685747 en
54743 0 cat_view 0 305 1782685738 en
54742 0 cat_view 0 305 1782685732 en
54740 0 cat_view 0 305 1782685722 en
54729 0 cat_view 0 305 1782685340 en
54728 0 cat_view 0 305 1782685335 en
54727 0 cat_view 0 305 1782685330 en
54723 0 view 415764 0 1782684105 en
54721 0 view 415764 0 1782684104 en
54722 0 view 415764 0 1782684104 en
54720 0 view 414408 0 1782684054 en
54718 0 view 414408 0 1782684053 en
54719 0 view 414408 0 1782684053 en
54714 0 view 444755 0 1782683988 en
54708 0 cat_view 0 287 1782679106 en
54707 0 cat_view 0 287 1782679101 en
54706 0 cat_view 0 287 1782679096 en
54705 0 cat_view 0 287 1782679091 en
54704 0 cat_view 0 287 1782679086 en
54702 0 cat_view 0 287 1782679076 en
54700 0 cat_view 0 287 1782679066 en
54699 0 cat_view 0 305 1782679061 en
54698 0 cat_view 0 287 1782679056 en
54697 0 cat_view 0 287 1782679050 en
54696 0 cat_view 0 287 1782679045 en
54695 0 cat_view 0 287 1782679042 en
54689 0 cat_view 0 305 1782678526 en
54686 0 cat_view 0 305 1782678512 en
54683 0 view 116427 0 1782678499 en
54678 0 cat_view 0 305 1782678476 en
54675 0 cat_view 0 305 1782678461 en
54672 0 cat_view 0 305 1782678446 en
54670 0 view 424436 0 1782671237 en
54669 0 view 424436 0 1782671233 en
54668 0 cat_view 0 305 1782671226 en
54667 0 cat_view 0 305 1782671221 en
54660 0 cat_view 0 305 1782671186 en
54659 0 cat_view 0 305 1782671181 en
54658 0 view 457702 0 1782671176 en