B, D is correct

The two alternatives to implement the integration and protect against malicious calls to the Heroku app's endpoint are:

- C. Create a Workflow Rule with an Outbound Message allowing the Heroku app to automatically store the resized images in Salesforce.
- D. Create a trigger that uses an @future Apex HTTP callout passing JSON serialized data and some form of pre-shared secret key, so that the Heroku app can authenticate requests and store the resized images in Salesforce.

Option C is a valid alternative because it uses an Outbound Message, which is a type of workflow action that sends a secure, configurable API message (in XML format) to a designated listener. The Outbound Message can include the product image data and a session ID, which allows the Heroku app to use the SOAP API to store the resized images back in Salesforce. The Outbound Message also supports digital signatures, which can be used to verify the authenticity of the message.

Option D is a valid alternative because it uses an @future Apex HTTP callout, which is a way to make an asynchronous HTTP request to an external service from Apex. The callout can pass the product image data and a pre-shared secret key, which is a string that is known only by the sender and the receiver, and can be used to encrypt or hash the message. The Heroku app can use the secret key to decrypt or verify the message, and then store the resized images back in Salesforce using the REST API.

The other options are not valid alternatives for the following reasons:

- Option A is incorrect because it assumes that the Heroku app can automatically reply back to the callout with the resized images, which is not possible. HTTP callouts are one-way requests that do not support bidirectional communication. The Heroku app would need to use another method, such as Salesforce APIs, to send the resized images back to Salesforce.
- Option B is incorrect because it uses an Outbound Message with a session ID, but does not specify how the H...