SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '527bad7b03c03954d612819af9b27974be80186e5b1259e221aa20cc354b79b2' 
  AND token = 'mgA2s60DVgP3ebd8p/mj5JRALBTytl5DSy0rcVz/cUk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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