continous deployments

Traditionally deploying a new release and making it live in production involves replacing the existing release with the new one, this leads to a period of downtime which may be considerable for large, monolithic applications. The solutions adopted to tackle this problem are usually some variation of the o called blue-green deployment process. The diagram below illustrates this set up in which all public traffic is routed through a reverse proxy (like Nginx or HAProxy) that forwards request to the correct release of the application (which then interacts with its correct instance of a database)