SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4a33674fd7111b8f7bfd91665d69f2d804671744126f5a472573a4e735137f84' 
  AND token = 'pYbTfWRrZ/s4jMwWw2KpVl+VaEPv7hs//UhAG0FHgJM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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