You are leading the DevOps team for a large$-$scale e$-$commerce platform that consists of numerous microservices. The platform is highly distributed, with critical services including user authentication, product catalog, checkout, and payment processing. The platform needs to be highly available, as even a few minutes of downtime can lead to significant financial loss. Recently, your team has been tasked with deploying a major update to the checkout service, which includes changes to both business logic and database schema.

Given this scenario, propose a deployment strategy that addresses the following:

$1.$ Zero downtime during the deployment process.

$2.$ Safe database migration to handle breaking changes.

$3.$ A way to test the new version in production while minimizing risk.

$4.$ Ensuring backward compatibility for dependent services during the transition phase. $[8$ Marks$]$