Hey @Pedro Antunes
Thanks for clarifying above. Based on what you've provided, definitely sounds like this is a cold start scenario where your app isn't completely ready to accept requests yet. It is recommended that you have at least 1 replica to avoid these sorts of issues, but I understand you want to scale from 0.
Having said that, if you're only experiencing this issue when you're starting with 0 replicas and the transition from activating to running is in the tune of minutes with a low number of concurrent requests, then we would need to work more closely with you to investigate further, just comment down below. However, if the startup time is minimal and response time is paramount for your application, then you may need to consider running at least 1 replica to avoid this.