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The code you shared should work. Are you getting an error or is the file not being created?

if  I split my stack into two; first to create the file,then second to read the file and use it, it works - I want to remove the file steps and just use the data in memory

```let private_key_encoded = "";
    service_account_key.privateKey.apply(k =&gt; private_key_encoded = k);```

Yea, this is a nuance to the async model within Pulumi. Can you share how you're wanting to use `private_key_encoded` ? I can help you get it working and explain what's happening if I can see more of your code.

```const user_data_template = readFileSync('./cloud-config').toString();
    const vars_map = {
        private_key_json: private_key_encoded
    }
    const compiled_user_data = _.template(user_data_template);
    const rendered_user_data = compiled_user_data(vars_map);```

so I'm using a template to render user-data for cloud-init

this key needs to be written to a specific location - I have similar (working) terraform code so essentially I'm translating from terraform

The `readFileSync` code also has to be inside the same `apply()` block. As written, that code is (potentially) being run before the `apply()` block. `private_key_encoded` is not updated by the time it is being used.