Contributed to the symfony/symfony repository by implementing keepalive support for the Doctrine Messenger transport, addressing premature message redelivery and enhancing workflow reliability. Developed a new keepalive method within the Connection class to refresh the delivered_at timestamp, ensuring messages remain active during long-running processes. Updated both DoctrineReceiver and DoctrineTransport to adopt the KeepaliveReceiverInterface, integrating this functionality into the existing message queue architecture. Comprehensive tests were added to validate keepalive behavior, rollback scenarios, and timeout configurations. This work demonstrated strong backend development skills, with a focus on PHP, Symfony, and database interaction to improve messaging durability and system robustness.