Exercises, Knowledge Checks & Phase Exit Turn the diagrams into working mental models before Phase 01 introduces tools and commands.
Book 6 · Active learning and assessment Course baseline: September 17, 2026 · Windows-first · Project-driven · Production-oriented
Contents 1. How to practice 6. Design scenarios
Phase 00 | Page 2 of 7
Phase 00 is complete only when you can reason without the diagram This book converts passive reading into active recall. Do the exercises before reading the answer guide. The goal is not perfect wording; the goal is correct ownership and causal reasoning.
1. What problem does a backend API solve that a purely browser-based application cannot safely solve? 2. Why is Prisma not the database? 3. Why does a valid JWT not automatically mean a user may edit every task? 4. What is the value of keeping Next.js and NestJS independent even inside one repository? 5. Why might Node 24 LTS be a better course runtime than Node 26 Current? 6. Why are major-version upgrades treated as separate projects?
For each responsibility, write the primary owning layer: browser/Next.js, NestJS, Prisma, PostgreSQL, Supabase Auth, TanStack Query, or CI/CD.
Phase 00 | Page 3 of 7
Scenario A - Create task A signed-in user enters “Prepare Q4 report” and clicks Create. Write the request journey from click to persisted row and back to visible UI. Name at least seven boundaries or responsibilities.
Scenario B - Unauthorized edit User A guesses the ID of User B’s task and sends a PATCH request manually. Where must the system reject the request? Why is hiding the button in the UI insufficient?
Phase 00 | Page 4 of 7
1. Add task priority. List every layer that may need to change. Do not write code. 2. Add workspace roles. Explain why the role should not be trusted from a browser form field. 3. Add a dashboard count. Decide whether the count is persistent truth, server state, or local UI state. 4. Add realtime comments. Explain why you would first build ordinary HTTP comments before adding realtime delivery.
Imagine Prisma 8 becomes stable halfway through Phase 20. Choose the best response and explain why:
1. Upgrade immediately because newer is always better. 2. Ignore all future security updates forever. 3. Keep the course on its locked Prisma version, record Prisma 8 as an ecosystem note, and plan a separate migration exercise after a stable milestone. 4. Mix Prisma 8 CLI commands into the existing Prisma 7 project.
Phase 00 | Page 5 of 7
On blank paper or a whiteboard, design the request path for: “An authenticated workspace member marks a task complete.”
□ Browser interaction. □ Next.js / React. □ Server-state layer. □ HTTP method and resource. □ Access token. □ NestJS route/controller. □ Token validation. □ Authorization/ownership or membership decision. □ Service rule. □ Prisma update. □ PostgreSQL. □ Response. □ Frontend cache/UI update. □ At least two possible failure points.
Can member delete project? NestJS authorization/business layer
Signed-in identity Supabase Auth; backend verifies token
Phase 00 | Page 6 of 7
Unauthorized edit The browser is not a trusted security boundary. The backend must verify the token, establish the caller identity, and check workspace membership/ownership/permissions before the update service performs the mutation. A hidden button improves UX but does not prevent a crafted HTTP request.
Prisma upgrade policy Choice C. The course baseline remains reproducible; the upgrade is treated as an explicit migration with changelog review, compatibility testing and a rollback plan.
□ I can explain Browser → Next.js → NestJS → Prisma → PostgreSQL. □ I can distinguish authentication from authorization. □ I understand why Supabase Auth and Supabase PostgreSQL solve different responsibilities. □ I understand why TanStack Query is not the database. □ I can explain why the course uses a version manifest. □ I know why Prisma 7.9.1 is a hard lock. □ I can describe TaskFlow’s growth from Todo to collaborative application. □ I can identify the most likely layer from an HTTP status or browser symptom. □ I completed the capstone diagram without copying the atlas.
Phase 01 moves from architecture to the development environment. We will verify Windows, PowerShell, Node 24 LTS, pnpm, Git, editor/tooling, PATH behavior and a reproducible project workspace - with explicit checkpoints before any application scaffolding.
Phase 00 | Page 7 of 7
Exercises and Phase Exit matters because it changes a real boundary in TaskFlow. The goal is to understand the inputs, owner, observable output, and failure modes before adding more abstraction.
Restate the goal of “Exercises and Phase Exit” as one observable behavior. Write the success signal before touching code.
Trace the boundary map: User intent → UI boundary → API contract → business rule → persistence → observable result. Mark the one boundary this lesson changes.
Inspect the current repository state and record the exact files, route, table, or runtime involved. Avoid creating an abstraction before you can name the existing owner.
Implement the smallest vertical slice. Add one coherent change, run the narrowest verification command, and read the output before continuing.
Connect the slice to TaskFlow’s phase artifact: A one-page architecture map plus an ADR-style note describing the responsibilities of Next.js, NestJS, Prisma, PostgreSQL/Supabase, and supporting infrastructure.. Verify behavior from the outside as a user or API client would.
Create one controlled failure that is safe to reproduce. Predict the symptom first, capture evidence, locate the earliest broken boundary, then fix only that cause.
Close the reference and rebuild or explain the core change from memory. Record what you would monitor or test before trusting the same change in production.
Input -> owner -> transformation -> observable output -> failure evidenceDo not copy this as a finished answer. Predict what each boundary does, type the smallest useful slice, run it, then compare the result with your prediction.
Return to the nearest observable boundary: input, network, process log, database, or rendered UI. Compare actual evidence with the predicted path.
Change one variable at a time and reproduce the original failure after the fix; otherwise you have correlation, not diagnosis.
Without copying the final source, create a second small scenario that applies “Exercises and Phase Exit” to a different TaskFlow resource or input. Write the acceptance criteria first, implement it, and provide the evidence that each criterion is satisfied.
Record the architecture decisions that should remain stable through later phases.
Use the smallest change that demonstrates this lesson. Stop after it works and capture evidence.Letting controllers call the database directly everywhere
Predict the symptom before causing the failure. Then locate the earliest boundary where reality diverges from expectation.Why does this responsibility live here, what input does it trust, what output proves success, and what would go wrong if another layer owned it?
If your explanation is vague, repeat the boundary trace before moving on.Close the reference. Reproduce the core idea from memory or explain the exact request/data flow aloud. Then check your diff or notes for accidental shortcuts that bypass validation, authorization, error handling, or verification earned in earlier phases.