Lesson 3 of 9

🏠 System Architecture

🎯 Grades 9–12 ⏱ ~30 minutes 🟡 Intermediate

What You'll Learn

What system architecture is and why architectural decisions matter
Common architecture patterns: centralized, distributed, layered, microservices
How to evaluate architecture trade-offs using a trade study

⚖ Architecture Trade Study

Rate how important each criterion is (1–5 weight), then score each architecture option (1–5). The tool computes weighted scores to help select the best architecture.

Criterion	Weight (1–5)	Centralized	Distributed	Microservices
Weighted Total	—	—	—	—

What Is System Architecture?

System architecture is the high-level structure of a system — the major components, how they relate to each other, and the principles guiding the design. Architecture decisions are the most consequential in engineering because they are the hardest to change later.

A good architecture makes requirements easy to meet and provides room for future growth. A bad architecture creates constraints that fighting against them costs more than building from scratch.

Architecture Patterns

Centralized: All functions managed by a single node. Simple to manage but single point of failure.
Distributed: Functions spread across multiple nodes. Resilient but more complex to coordinate.
Layered: System divided into horizontal layers (e.g., presentation, logic, data). Each layer only interacts with adjacent layers.
Microservices: System built from small, independent services communicating via APIs. Highly scalable and maintainable but high operational complexity.
Event-driven: Components communicate by publishing and subscribing to events. Decoupled and scalable for real-time systems.

Architecture Trade Studies

When multiple architecture options exist, a trade study evaluates them objectively. The process:

Identify evaluation criteria (performance, cost, reliability, maintainability, scalability)
Assign weights to criteria based on stakeholder priorities
Score each option on each criterion
Compute weighted totals
Select the highest-scoring option (or justify choosing otherwise)

💻

Netflix's Architecture Evolution

Netflix started with a monolithic (centralized) architecture. As it grew to 200 million users, they migrated to microservices — over 1,000 independent services. This allows teams to deploy updates without affecting other services and lets them scale individual functions independently. The migration took years and was extremely costly, illustrating why getting architecture right early matters so much.

Quick Check

1. Why are architecture decisions especially consequential in systems engineering?

AThey determine the programming language used

BThey are the hardest to change later and affect everything downstream

CThey only affect performance, not reliability

DThey are usually made at the end of the project

2. Which architecture pattern is most resilient to single-node failure?

ACentralized

BDistributed

CLayered

DMonolithic

3. In a layered architecture, how do layers interact?

AAny layer can communicate directly with any other layer

BEach layer only interacts with adjacent layers

CAll layers communicate through a central message bus

DLayers never communicate — they operate independently

4. What is the purpose of an architecture trade study?

ATo determine the project budget

BTo select the most popular technology

CTo objectively evaluate multiple architecture options using weighted criteria

DTo document the final architecture chosen by the customer

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