Django REST framework, serializer performance degradation

Question

I have a simple list API view which is using serializer:

class ListCreateDeploymentView(
    generics.ListCreateAPIView
):
    permission_classes = (IsAuthenticated,)
    renderer_classes = [JSONRenderer]
    content_negotiation_class = IgnoreClientContentNegotiation

    def get_queryset(self):
        queryset = Deployment.objects.all()
        return queryset

    def list(self, request, version):
        queryset = self.get_queryset()
        serializer = DeploymentListSerializer(queryset, many=True)
        data = serializer.data
        return Response(data)

Serializer is simple:

class DeploymentListSerializer(serializers.ModelSerializer):
    class Meta:
        model = Deployment
        fields = (
            'id',
            'query',
            'config',
            'started_at',
            'finished_at',
            'status',
            'project',
        )
        read_only_fields = (
            'id',
            'query',
            'config',
            'started_at',
            'finished_at',
            'status',
            'project',
        )

Then I do a local load test with 10 users and delay 1s each execution so target rps is 10 req/s and see this picture with a clear performance degradation after few minutes

What means If I open 10 tabs in browser with ajax request every second to this endpoint the server will get unresponsive in a minute:

Then I used recommendations from here and used read-only regular serializer:

class DeploymentListSerializer(serializers.ModelSerializer):
    # commands = CommandListSerializer(read_only=True, many=True)
    # clients = ClientSimpleSerializer(read_only=True, many=True)
    id = serializers.IntegerField(read_only=True)
    query = serializers.CharField(read_only=True)
    config = serializers.CharField(read_only=True)
    started_at = serializers.DateTimeField(read_only=True)
    finished_at = serializers.DateTimeField(read_only=True)
    status = serializers.IntegerField(read_only=True)
    project = serializers.CharField(read_only=True)
    class Meta:
        model = Deployment
        fields = (
            'id',
            'query',
            'config',
            'started_at',
            'finished_at',
            'status',
            'project',
        )

The situation became even worse: Finally, if I remove serialization:

    def list(self, request, version):
        queryset = self.get_queryset()
        data = queryset.values(
            'id', 'query', 'config', 'started_at', 'finished_at',
            'status', 'project'
        )
        return Response(data)

And do same test again the performance getting much better(expected), but also stable:

The problem is I need serialization because the task is a bit more complicated and I need to return nested objects, but it`s already falling on such an easy example.

What do I wrong?

UPD: same bad picture if I use the function-based view:

@api_view(['GET'])
def get_deployments(request, version):
    queryset = Deployment.objects.all()
    serializer = DeploymentCreateSerializer(queryset, many=True)
    data = serializer.data
    return Response(data)