SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '960fce827f02d094fea2b479720ffc30a4bf543813b695da518e5685f2d89f34' 
  AND token = 'b8QZxmuvIx651QLdIVSeQvDfduvfw7vTYgDI9pBxwX8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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