Change Data Capture (CDC) is the most appropriate solution as it is specifically designed for this use case. It is an event-driven, asynchronous mechanism that automatically publishes change events (for create, update, delete, and undelete operations) for Salesforce objects. The homegrown application can subscribe to the ContactChangeEvent stream using a CometD client to receive near-real-time updates. This approach is highly scalable, durable, and meets all requirements without requiring custom Apex code to publish the events, making it the most precise and standard solution for data synchronization.

1. Salesforce Change Data Capture Developer Guide

"Change Data Capture Basics": "Change Data Capture is a streaming product on the Lightning Platform that enables you to efficiently integrate your Salesforce data with external systems. With Change Data Capture

you can receive near-real-time changes of Salesforce records

and synchronize corresponding records in an external data store." This directly supports the use of CDC for synchronizing an external application.

2. Salesforce Platform Events Developer Guide

"Platform Event and Change Data Capture Allocations": "Change Data Capture is the recommended solution for record data changes. If your app requires only record data changes

use Change Data Capture. Platform events are more flexible and can be used for any business process." This highlights that for replicating record changes

CDC is the superior and more specific choice.

3. Salesforce Integration Patterns and Practices

"Data Synchronization": This document outlines various patterns. CDC falls under the event-based synchronization pattern

which is described as ideal for near-real-time updates triggered by data changes. In contrast

ETL is categorized under batch data synchronization

which is not event-driven. The @future method would be a form of Remote Procedure Invocation

which is a point-to-point pattern

not a publish-subscribe pattern.