SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5cc881bf6322a28e23a68b8f7eb73e77137c7d776adb5c675280c91536de73f1' 
  AND token = '4MKvGawoCLFgZRmXWoaIiJOYBarcAioCXHgNHM4MiI4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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