Would you voluntarily spend another five hours on this kind of problem? Why?
Backend Engineering · 90–120 min
Build, break and explain a tiny API
Feel data modeling, validation, failure and debugging—not only the happy path.
Start the experiment01 · Setup
What you need
- Basic programming and a local runtime.
You may stop when the timebox ends. An incomplete result is still useful evidence.
02 · Task
The work sequence
- 01
Create three endpoints for a tiny book-lending service.
- 02
Store books and loans in memory or SQLite; define invalid states.
- 03
Add validation and one automated test for a rejected loan.
- 04
Introduce a duplicate-loan bug, use logs to find it, then fix it.
03 · Pay attention
Watch your reaction, not only the output
- Did modeling the rules feel satisfying?
- Did debugging become more interesting after evidence appeared?
Plot twist
Difficulty does not mean the career is a bad fit. The useful question is whether curiosity returned after the difficulty.
04 · Reflect
Three honest questions
Which part gave you energy, and which part drained it?
What evidence—not a salary video—would you gather before choosing this path?
This site does not save your answers. Put them in your own notebook if useful.
05 · Where to go next