<p>I have two network policies (one with pod selector app=db and the other with app=proxy) and I have one pod to apply both network policies, the pod config doesn't allow to have 2 different labels with the same key app.</p>
<p>How can I do it in this case without modifying any network policies?</p>

<p>If the pod/label/app selector is the only selector in each policy then it's not possible. The net policy probably needs a   <code>matchExpressions</code> selector then a new label.</p>
<p>Ingress and Egress rules can supply an array of <code>podSelector</code>s for the network targets, or similar <code>matchExpressions</code></p>
<pre><code>spec:
  podSelector:
    matchExpressions:
      - key: role
        operator: In
        values: [ &quot;db-proxy&quot;, &quot;db&quot; ]
</code></pre>
