Payment System
Design a payment processing system handling transactions, idempotency, reconciliation, fraud detection, and multi-currency support. Tests exactly-once semantics, distributed transactions, saga pattern, and financial system reliability.
Cheat Sheet
Key concepts, trade-offs, and quick-reference notes for Payment System. Everything you need at a glance.
Problem Patterns
Recurring design patterns and approaches. Learn to recognize which pattern fits which requirement.
Timed Challenge
Simulate a real interview. 30-45 minute design challenge with structured prompts and evaluation criteria.
Interview Questions
Real interview questions from top companies. Filtered by difficulty, company, and sub-topic.
Anti-Patterns
Common design mistakes candidates make. Wrong approaches vs correct approaches for each trap.
Visual Solutions
Step-by-step animated walkthroughs of system design solutions with architecture diagrams and key insights.