Reasoning Checkpoint
A design challenge, worked through in writing — no auto-grading, just a real attempt.
The Challenge
This is the year in one exercise. John asks Anna to put the whole system on one page, from memory, for the new junior who starts on Monday.
Use a different example from Olivia's purchase: a fan opens the BlueTicket app and views their ticket for tonight's show (GET /v1/tickets/tk_501).
What Your Page Needs
- Draw (or list) the complete request journey for viewing the ticket, from the user to the response and back, with one sentence per step.
- Draw the stack underneath one of the machines involved: application → runtime → operating system → hardware → network.
- Next to each step and layer, write the number of at least one Act where you learned about it — try to use every Act at least once.
- Mark three places where something could go wrong in this journey, and the lesson from this year that protects against it.
- Write one sentence about what changed for you between Act 01 and Act 26.
Stuck? A Few Hints
- Viewing a ticket is a read: think about the cache, authorization and what the database is asked.
- Don't forget the journey back: the response, the browser and the user.
- Practices like Git, testing, CI/CD and monitoring sit around the journey rather than inside it.
Before You Move On
If your page covers the journey, the stack underneath and the practices around it, you have something many working developers never build: the whole map. Everything you learn from here — a new language, framework or cloud service — is just more detail on a map you already have.