Google Analytics is a free web analytics service that tracks and reports website traffic.
Google Tag Manager is a tag management system (TMS) that allows you to quickly and easily update measurement codes and related code fragments collectively known as tags on your website or mobile app.
Kong is an open-source API gateway and platform that acts as middleware between compute clients and the API-centric applications.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.