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SOLID principles · designlab

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Part 1 · Module 2

SOLID principles

Six rules that keep classes small, stable and easy to test: SRP, OCP, LSP, ISP, DIP, and the DRY/KISS/YAGNI heuristics.

0 of 6 lessons38 min

2.1Single responsibilityUp next7m
2.2Open/closed principle6m
2.3Liskov substitution6m
2.4Interface segregation6m
2.5Dependency inversion7m
2.6DRY, KISS, YAGNI and the Law of Demeter6m
LabRefactoring the Monolithic Invoice ServiceFinish “Designing the Media Library Hierarchy” first35m

Practice what this module teaches

Shopping Cart Domain LLDModel cart mutations, version checks and reproducible price quotes.Intermediate40 min Logging Framework LLDCompose structured logging, redaction and bounded asynchronous output.Intermediate40 min Dependency Injection Container LLDResolve object graphs with scopes, cycle detection and deterministic cleanup.Advanced

45 min

Coupon Rule Engine LLDEvaluate composable discount rules with exact arithmetic and atomic redemption limits.Intermediate45 min