SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ac5e625430c61861432b7a2763171b23e5802817bedfc4a571c960a60a49babc' 
  AND token = 'fa6K8fJmazuD5PNdlKAvfbliBZUiIcOvxhj3hM9jzL8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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