Knative Ideal Architecture Setup / Activator Instability

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Hey, we’ve been running into some unexplained instability with our Knative setup and are wondering whether our current architecture is ideal for production reliability.

We’re currently using Kourier along with Istio as an additional security layer. Is this a recommended setup, or would a simpler architecture—such as using Kourier alone—generally be preferable?

The recurring issue we’re seeing is that the Knative Activator appears to fail or become a bottleneck. When this happens, requests stop flowing end-to-end, even though the backend pods have already scaled up and there is still queued work waiting to be processed. In these cases what fixes the issue is restarting all our knative components. We've also seen the case where activator is pointing to a very old revision that isn't even deployed.

This has us questioning whether our current request path and scaling configuration are contributing to the problem. Has anyone encountered similar behavior?

We’d especially appreciate recommendations around:

Whether Kourier + Istio is a reasonable architecture versus using Kourier alone
Activator configuration or tuning
Concurrency and target settings
Ingress configuration/choice
Scaling class or autoscaling adjustments
Other approaches for ensuring traffic continues flowing reliably during load spikes

Start by tracing the request path through Kourier, Istio, and the Knative Activator, then review the reported concurrency, target, ingress, and autoscaling settings. Compare the behavior when the Activator points to an old revision and collect logs or a reproducible configuration; done requires a confirmed cause and a documented production architecture or configuration recommendation.

Written by the indexing model from the issue text.