Show the shape of the system
With scope, API, and data model in hand, you draw the high level architecture. This is the major components and the path a request takes through them. It gives the interviewer a map and gives you a frame for the deep dive.
Common building blocks
- Clients and a load balancer at the edge.
- Application services that hold the logic.
- Databases for durable storage.
- Caches for hot reads.
- Queues for async work.
Trace a request
Keep it readable
- One box per responsibility so the picture stays clean.
- Label the edges with what flows between components.
- Walk a read and a write to show the diagram actually works.
- Resist detail here, since the deep dive comes next.
Why this order
Because you defined the API and data first, each box has a reason to exist. You can point at an endpoint and trace it through the load balancer, service, cache, and database, proving the design serves the requirements.
Key idea
Draw the major components and trace a request end to end so the interviewer sees a coherent system before you zoom into any single part.