Challenges

Payment System Double-Billing (Array)

Merge Overlapping Server Downtimes (Intervals)

API Rate Limiter — Sliding Window (Queue)

CI/CD Pipeline Dependency Resolution (Graphs)

Live Stock Ticker — Top K Volatile (Heaps)

Distributed Hash Ring — Consistent Hashing (Binary Search)

Driver-Rider Proximity Matching (K-D Tree)

Fraud Ring Detection (Union-Find)

Recommendation Cache — LRU (HashMap + DLL)

Log Stream Pattern Search (Aho-Corasick)

Ledger Reconciliation (Two Pointers)

Webhook JSON Payload Validator (Stack)

Git Bisect Memory Leak (Binary Search)

Peak Error Rate (Sliding Window)

Microservice Blast Radius (Graph BFS)