Two Heaps Interview Pattern
6 min read The Two Heaps Pattern Two heaps maintain the lower and upper halves of a data stream, allowing O(1) access to […] Read article
Algorithms, Coding Interview Questions, Heap
System Design
Secret Manager System Low-Level Design
7 min read What is a Secret Manager? A secret manager stores and distributes sensitive credentials (API keys, database passwords, TLS certificates, OAuth Read article
System Design
Log Aggregation System Low-Level Design
6 min read What is a Log Aggregator? A log aggregator collects logs from distributed services, normalizes them, stores them for search, and Read article
System Design
Rate Limiting System Low-Level Design (Token Bucket, Leaky Bucket)
6 min read Why Rate Limiting? Rate limiting protects services from abuse, ensures fair usage, and prevents cascading failures from traffic spikes. Applied Read article
Algorithms, Coding Interview Questions, Data Structures
Matrix Traversal Interview Patterns
7 min read Grid Traversal Fundamentals Most matrix problems involve: (1) BFS from one or multiple source cells, (2) DFS to explore connected Read article
System Design
Webhook Delivery System Low-Level Design
6 min read What is a Webhook? A webhook is a user-defined HTTP callback. When an event occurs in a platform (payment succeeded, Read article
System Design
Multi-Region Architecture Low-Level Design
6 min read Why Multi-Region? Single-region deployments fail entirely during a cloud provider AZ or region outage. Multi-region provides: (1) High availability — Read article
System Design
Invoice and Billing System Low-Level Design
7 min read Requirements Generate invoices for subscriptions and one-time purchases Support multiple billing cycles: monthly, annual, usage-based Apply discounts, taxes, and proration Read article
System Design
Search Suggestions (Autocomplete) System Low-Level Design
6 min read Requirements Return top-k (k=10) query suggestions as a user types, within 100ms Suggestions ranked by search frequency or relevance score Read article
System Design
Content Feed System Low-Level Design
6 min read Requirements Generate a personalized feed of posts ranked by relevance/recency for each user Supports follow relationships: see posts from users Read article
System Design
Online Auction System Low-Level Design
7 min read Requirements Users can create auction listings with a start price, reserve price, and end time Users place bids; highest bid Read article
System Design
Location Tracking System Low-Level Design
6 min read Requirements Track real-time location of mobile assets (drivers, delivery couriers, field workers) 1M active devices sending location updates every 4 Read article
Algorithms, Coding Interview Questions, Data Structures
Ordered Map (TreeMap / SortedList) Interview Patterns
6 min read When to Use an Ordered Map (Sorted Dict / TreeMap) An ordered map maintains keys in sorted order with O(log Read article
System Design
Data Pipeline System Low-Level Design
6 min read What is a Data Pipeline? A data pipeline is a sequence of data processing steps: collect → transform → store Read article
System Design
Coupon and Discount System Low-Level Design
6 min read Requirements Create and manage discount coupons (percentage, fixed amount, free shipping) Apply coupon to a cart: validate, compute discount, prevent Read article