C4 Container View for a Booking Platform

This C4 container diagram breaks a booking platform into the applications and services that do the work at runtime. Customer and administrator browsers use a web application, which calls the booking API. The API owns booking data and integrates with search, payment and email services. It is a useful middle-level view for a product team because it says more than a system context diagram without exposing classes, methods or infrastructure settings. The arrows show meaningful dependencies rather than network topology. Add a mobile app, cache, queue or identity provider when those are real containers or external services in the platform. Use a component diagram next to explain what is inside the booking API.