Metrics

Four standard steps for system design interview. However, I would think about them wider: as about four initial steps to design the software.

• Step 1. Understand the problem and establish design scope
• Step 2. Propose high-level design and get buy-in
• Step 3. Design deep dive
• Step 4. Wrap up

The chapter 3 of the book discovers details about each step, good questions to ask (to think about), DO’s and DONT’s. It also shows good example of the process of designing a news feed system.

A great generic plan for scaling any app from zero to millions of users.

• Single server setup
• Selection and usage of database
• Vertical scaling vs horizontal scaling approaches. And why you should prefer horizontal
• Adding load balancer for horizontal scaling
• Adding database replication for horizontal scaling
• Adding cache
• Adding CDN
• Stateless vs Stateful architecture and using external state storage
• Adding extra Data Centers
• Adding Message queue
• Adding Logging, Metrics, and Automation
• Scaling database (sharding)
• and futher steps…

All of these is carefully but briefly disclosed in the Chapter 1 of the book:

The book club of our company has chosen a new wonderful book for reading:

Robert Martin - Clean Architecture - a Craftsman’s Guide to Software Structure and Design

Fourth part of the book is about principles of combining components into software systems.

This part is more interesting. It contains:

• Overview of components history: Relocatability, Linkers
• Three principles of Component Cohesion
  • REP: The Reuse/Release Equivalence Principle
  • CCP: The Common Closure Principle
  • CRP: The Common Reuse Principle
• Three principles of Components Coupling
  • ADP: The Acyclic Dependencies Principle
  • SDP: The Stable Dependencies Principle
  • SAP: The Stable Abstractions Principle

I especially enjoyed this chapter because of presented metrics that could be used to measure(!) good software design (more precisely, how do you follow some design principles)