SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b10a6e7be1d86e44462be811db8cdc079752ee98e7048a8df17d776acb918b02' 
  AND token = 'GuM5eltWMHSZOku2QjOKe91oJZsh89vxnAic3nMhepw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}