Top 50 design patterns Interview Questions

Implement an Observer-pattern event dispatcher that delivers topic events to subscribed observers in registration order.

clean codeabstractiondesign patternsAccentureChetu

Implement a Singleton class that preserves one instance, initializes state once, and remains safe under concurrent construction.

clean codeabstractionProgrammingAmerican ExpressEEcolab

Implement a configurable message formatter using Strategy and Factory design patterns.

clean codeabstractiondesign patternsNagarroCiti

Simulate trailing-edge debouncing for Dream11 search events using timestamps and a pending event.

debouncingdesign patternsDDream11Intercontinental Exchange Holdings

Create dependency-safe parallel deployment batches for assemblies using topological sorting and deterministic scheduling.

application developmentmultithreadingasync processingAveva

Model line items, discounts, and orders with composable classes and calculate a discounted order total.

clean codeabstractiondesign patternsPrincipal Financial Group