Tutorials System Design Tutorial
Design Patterns for Scalable Software — Complete Guide
Design Patterns for Scalable Software — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of System Design Tutorial on Toolliyo Academy.
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System Design Tutorial · Lesson 72 of 100
Design Patterns for Scalable Software
Basics ✓ → Scale ✓ → Interview
Interview · 3 — Case studies · ~10 min · Module 8: Low-Level Design
What is this?
Design patterns are reusable object-structure recipes — Strategy, Adapter, Observer, Circuit Breaker (stability), etc.
Why should you care?
ShopNest teams move faster when they share names for common structures instead of reinventing.
See it live — copy this example
Sketch the architecture on paper. These lessons focus on concepts and trade-offs.
Strategy: shipping cost calculators
Adapter: wrap legacy warehouse SOAP as IWarehouse
Circuit Breaker: protect Inventory HTTP client
Observer/events: cache listeners on price updatesRun Example »
This lesson uses terminal or setup steps. Run commands on your computer — the live editor appears on coding lessons.
What happened?
- Patterns are tools, not goals.
- Prefer clear names in code reviews.
- Stability patterns matter as much as GoF classics in distributed apps.
Practice next
- Apply Strategy to ShopNest shipping.
- Adapt one legacy dependency.
- Add a circuit breaker on a flaky call.
- Factory for notification channels.
- Retry with jitter as a policy object.
Remember
Shared pattern vocabulary. Use when they simplify. Include resilience patterns.
Shipping strategies
ShopNest picks courier cost via Strategy.
Outcome: New courier = new class, not a giant switch forever.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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