How to study with this course

Read this once (5 minutes). After that, the loop in section 2 is all you need.

1. Setup (once)

uv sync                                # install the tooling
cp learner.example.yaml learner.yaml   # your pace and dates (optional)
uv run de doctor                       # every row should say OK; follow any fix it prints

Later tracks need Kafka, Flink, Paimon or Fluss. Fetch them only when you reach that track (scripts are in labs/README.md). uv run de web serves the course in your browser, but you run and grade exercises in the terminal.

2. The loop

Every module works the same way:

Step	What you do	Command
1	Find what is next	de next
2	Read the lesson	content/<TRACK>/<MODULE>/lesson.md
3	Start an exercise	de start <EXERCISE_ID>
4	Edit your code in workspace/ and grade it. Repeat until it says PASSED	de test
5	Take the quiz	de quiz <MODULE_ID>
6	Explain the module in your own words (explain.md), then rehearse drills.md	–

Do not skip step 6. It is what turns "the tests pass" into an answer you can give in an interview.

3. What is in a module

content/FND/FND-01/
├── lesson.md        read first: why it exists → how it works → from your world → when NOT to use it
├── exercises/       graded coding work; do them in number order
├── quiz.yaml        take it with `de quiz FND-01` (answers are inside, so don't open it)
├── explain.md       write ~200 words, then tick the self-check rubric (aim for 5 of 6)
└── drills.md        interview questions: cover the answer, say yours out loud, compare

4. Doing an exercise

de start FND-01/01-scale-up-vs-out    # copies the starter to workspace/FND-01/01-scale-up-vs-out
de test                               # grades the exercise you started last

• The exercise README.md is the spec. Read What the tests check closely.
• Edit only files in workspace/. All tests fail on a fresh starter; that is expected.
• Stuck? de hint gives a nudge. --level 2 and --level 3 get closer to the answer.
• de solution unlocks after a pass or 3 failed attempts. Read it after you pass too, and compare it with your code.
• To start over, delete the workspace folder and run de start again.

Don't open these folders. They contain answers: solution/, alt_solutions/, mutants/.

5. Build-your-own challenges

Each core track ends with one challenge. You write a single codebase that grows over several stages, and each stage has its own tests.

After	Challenge	You build
SPK	SPK-BYO	A columnar query engine
LKH	LKH-BYO	An Iceberg-like table format
KFK	KFK-BYO	A Kafka-protocol broker
FLK	FLK-BYO	A stream processor with watermarks and checkpoints

de start SPK-BYO       # stage 1
de test                # this stage plus all earlier ones
de start SPK-BYO/02    # next stage, once stage 1 passes

de next does not suggest BYO stages, so start them yourself at the end of each track. de hint and de solution don't work for BYO stages yet. Hints are in each stage's stage.yaml, and the reference is in its solution/ folder.

6. Order

Follow the roadmap: FND → SPK → LKH → JVM → KFK → FLK → STH. de next respects prerequisites for you. If you already know a module, take its quiz first, and if you pass, add it to tracks.skip_modules in learner.yaml.

7. A weekly rhythm (6 h/week)

Session	Time	Do
Wed	1.5 h	Read the next lesson; start the first exercise
Sat	2.5 h	Finish the exercises; read the solution; take the quiz
Sun	2 h	explain.md and drills.md; redo last week's misses

Stuck for more than 30 minutes? Take the next hint. Run de plan after changing pace or target_date in learner.yaml to see your projected finish date.

8. Where your progress lives

progress.json (grades), workspace/ (your code) and learner.yaml (your profile) are gitignored, so git pull never conflicts with your work and nothing is uploaded. To keep them, commit them in a fork with git add -f. To move machines, copy those paths.

The tick marks on the website's roadmap are separate: they live in your browser only.

9. Commands

Command	Use
de status	Passed/total per track, and the current exercise
de next	Next exercise with its prerequisites met
de start <ID>	Begin an exercise or BYO stage
de test [ID]	Grade the current (or given) exercise
de hint [--level N]	Hints 1–3
de solution [ID]	Reference solution (after a pass or 3 failures)
de quiz <MODULE>	Interactive quiz; best score saved
de plan	Projected finish date from learner.yaml
de doctor	Environment check