While a lambda is still processing (archive unpacking etc), the lambda state should be set to "Pending" (currently "Active") and invocations to that lambda should fail (currently, it can end up in a inconsistent state in this case, like lambdas being executed without layers).

Lambda state should reflect the current internal state, and invocations should fail if not active.
"DestinationConfig": {
                "OnSuccess": {"Destination": str(response.on_successful_invocation)},
                "OnFailure": {"Destination": str(response.on_failed_invocation)},
            },
        }
    )
@app.route("/2019-09-25/functions/<function>/event-invoke-config", methods=["GET"])
def get_function_event_invoke_config(function):
    """Retrieves the configuration for asynchronous invocation for a function
    ---
    operationId: GetFunctionEventInvokeConfig
    parameters:
        - name: 'function'
          in: path
        - name: 'qualifier'
          in: path
        - name: 'request'
          in: body
    """
    region = LambdaRegion.get()
    try:
        function_arn = func_arn(function)
        lambda_obj = region.lambdas[function_arn]
    except Exception:
        return not_found_error("Unable to find Lambda function ARN %s" % function_arn)
    response = lambda_obj.get_function_event_invoke_config()
    if not response:
        msg = "The function %s doesn't have an EventInvokeConfig" % function_arn
        return not_found_error(msg)
    return jsonify(response)