SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '566e242843726270534d4fdddc9304da1dcfee6c9835a5241972623216a40226' 
  AND token = 'S7XRgaJUFhgkld726kRaiZoI4Z8mV34zDpZkLgDVuVo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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