Practice · Architecture and Design for Change

Q1

Which decision is most clearly architectural?

A Whether StudyBuddy is one deployable application or a set of independently deployed services B The wording of an error message C The font size of the course titles D The name of a local variable in PostValidator

Q2

Architecture is driven mainly by…

A the number of features B the favourite framework of the team lead C quality attributes such as availability, performance, security and maintainability, plus constraints D the colours of the user interface

Q3

A change to the posts database table forces changes in the Android screens, the web pages and the notification code. This indicates…

A high cohesion B a microservice architecture C good information hiding D high coupling — many modules depend on the internal data structure

Q4

A class Utils contains methods for date formatting, sending emails, computing quiz scores and resizing images. Its main design problem is…

A too few methods B low coupling C it is not a microservice D low cohesion — its parts do not belong together

Q5

According to Parnas's information-hiding principle, how should modules be chosen?

A Each module has exactly 100 lines B One module per developer C Each module hides a design decision that is likely to change, behind a stable interface D One module per step of the processing flowchart

Q6

Which is the best example of dependency inversion in StudyBuddy?

A All classes are in one package. B QuestionController receives a Tutor interface; VendorXTutor, VendorYTutor and FakeTutor implement it. C QuestionController creates a VendorXClient with new and calls its HTTP methods directly. D The database calls the controller.

Q7

Why does a FakeTutor implementation make testing easier?

A It removes the need for tests. B It improves the real answers. C It makes tests run on the real AI provider. D Tests become fast, free, deterministic and independent of the network and provider.

Q8

Every Tutor implementation must either return an answer or throw TutorUnavailableException — never return null. Which SOLID principle does this protect?

A Single responsibility B Liskov substitution — any implementation can be used wherever a Tutor is expected C Interface segregation D Open/closed

Q9

For a 5-student team building StudyBuddy in one semester, which architecture is most appropriate?

A A single 20,000-line class B A separate database per screen C A modular monolith with clear internal modules and the AI provider behind an interface D Nine microservices with a message broker and Kubernetes

Q10

Which problem do microservices mainly solve?

A Allowing many teams to develop, deploy and scale parts of a large system independently B Removing the need for a database C Slow compilers D Making small projects simpler

Q11

In a layered architecture (presentation → service → domain → data), which dependency is a violation?

A The presentation layer calls the service layer. B The data-access layer calls a class in the presentation layer. C The service layer calls the domain layer. D The domain layer uses its own classes.

Q12

StudyBuddy publishes a PostReported event; the moderation module adds the post to the queue, the notification module informs the TA, and the statistics module counts it. What style is this, and what is its main weakness?

A Waterfall; too much documentation B MVC; fat controllers C Event-driven; the overall flow is harder to follow and debug D Layered; slow

Q13

Buddy calls an external AI service that sometimes hangs for minutes. Which tactic is the first to add?

A A timeout (e.g., give up after 10 s) with a fallback message B Adding more RAM to the server C Removing error handling D Retrying immediately forever until it works

Q14

What does a circuit breaker do?

A Restarts the server every night B Limits the number of students C Encrypts traffic to the AI provider D After repeated failures it stops calling the failing service for a while and fails fast, then lets a trial call through to check recovery

Q15

Why are retries done with back-off (e.g., 1 s, 2 s, 4 s) rather than immediately and endlessly?

A Back-off makes answers more accurate B To make users wait longer C Because Java cannot retry immediately D Immediate endless retries from many clients can overload a struggling service; spacing and limiting them gives it time to recover

Q16

Forty students ask Buddy "What is polymorphism?" the night before the midterm. Which tactic reduces cost and waiting time?

A Calling the AI provider 40 times in parallel B Removing the question box C Asking each student to wait 10 minutes D Caching answers to identical questions for a limited time (TTL), with an eviction policy such as LRU

Q17

Module board depends on 3 modules and 1 module depends on it. What is its instability I = Ce / (Ca + Ce)?

A 0.75 B 0.25 C 1.33 D 3

Q18

StudyBuddy sends notifications through a long switch on the channel type (PUSH, EMAIL). Adding WeChat requires editing that switch in four places. Which principle does a Notifier interface with one class per channel restore?

A None; the switch is the better design B Open/closed — new channels are added by adding a class, without modifying existing code C Liskov substitution D Interface segregation

Q19

Why are dependency cycles (A → B → C → A) harmful?

A They are only a style issue. B They improve cohesion. C None of the modules in the cycle can be understood, tested, reused or changed independently. D They make compilation impossible in all languages.

Q20

Which sections does a classic ADR (Nygard) contain?

A Title, status, context, decision, consequences B The names of people who disagreed C Only the code that implements the decision D Meeting minutes of every discussion

Q21

A year later, the team replaces the decision in ADR-003. What should they do with ADR-003?

A Move it to a private folder B Keep it, mark it "Superseded by ADR-011", and write ADR-011 with the new decision C Delete it D Edit it so it describes the new decision

Q22

What is the main idea of retrieval-augmented generation (RAG) for Buddy?

A Let the model answer from its general knowledge only B First retrieve relevant passages from the instructor's course files, then ask the model to answer only from them and cite them C Train a new AI model from scratch for each course D Store every student's chat in the model

Q23

Why should Buddy's prompt template be versioned configuration with a controlled release process, instead of text anyone can edit live?

A A prompt change can change behaviour for every user at once — like CrowdStrike's "just configuration" update — so it needs testing, staged rollout and rollback. B Prompts are secret passwords. C Prompts cannot be stored in files. D It makes the AI provider cheaper.

Q24

An AI assistant proposes, for StudyBuddy, 9 microservices, Kafka, Kubernetes and a database per service. What is the best engineering response?

A Evaluate it against StudyBuddy's quality attributes, team size, skills, budget and hosting constraints — it is likely over-engineered; record the chosen alternative and reasons in an ADR. B Ask the AI for an even bigger architecture. C Implement half of it to compromise. D Accept it; AI suggestions reflect best practice.

Q25

Which is a sensible output guardrail for Buddy?

A Remove all code from all answers B Translate every answer into five languages C Check that the answer cites at least one retrieved course passage, and block complete solutions for exercises tagged as graded D Make every answer longer than 500 words

Q26 Short answer

Explain coupling and cohesion and, for each, give one concrete sign in code that it is bad, using StudyBuddy examples.

Q27 Short answer

Describe the three states of a circuit breaker (closed, open, half-open) and when it moves between them. Why is it useful for Buddy's calls to the AI provider?

Q28 Short answer

Write an ADR (title, status, context, decision, consequences) for: "StudyBuddy will be built as a modular monolith, not as microservices."

Q29 Short answer

Draw or describe Buddy's request flow with RAG and guardrails, and explain what each step protects against.

Q30 Short answer

List five things in StudyBuddy that are likely to change in the next two years and, for each, the module or interface that should hide it (information hiding).