5 min read String Fundamentals for Interviews Strings are immutable in Python and Java — concatenating in a loop is O(n^2). Use a […] Read article
7 min read Core Entities Poll: poll_id, creator_id, question, poll_type (SINGLE_CHOICE, MULTIPLE_CHOICE, RANKED, RATING), status (DRAFT, ACTIVE, CLOSED), is_anonymous, allow_change_vote, visibility (PUBLIC, PRIVATE, Read article
6 min read Geospatial Data Fundamentals Geospatial queries are common in production systems: “find the 10 nearest restaurants,” “is this user inside a Read article
7 min read Core Entities Cart: cart_id, user_id (NULL for guest), session_id (for guest carts), status (ACTIVE, ABANDONED, CHECKED_OUT), currency, created_at, updated_at, expires_at. Read article
7 min read Trie Fundamentals and Implementation A trie (prefix tree) stores strings character by character, sharing prefixes among strings. Each node represents Read article
6 min read Binary Search Fundamentals Binary search finds a target in a sorted collection in O(log n). The key insight: at each Read article
6 min read Core Entities Home: home_id, owner_id, name, address, timezone, created_at. Room: room_id, home_id, name, floor_number. Device: device_id, home_id, room_id, name, type Read article
6 min read Why Distributed Caching? A single application server’s in-memory cache is lost on restart and not shared across instances. A distributed Read article
6 min read What is an API Marketplace? An API marketplace (like Stripe, Twilio, RapidAPI, or AWS API Gateway) lets external developers discover, Read article
6 min read Core Entities Tenant: tenant_id, name, slug, plan, custom_domain, storage_quota_gb, created_at. (Multi-tenant: each customer organization is a tenant with isolated content.) Read article
6 min read Union-Find Data Structure Union-Find (also called Disjoint Set Union, DSU) tracks which elements belong to the same connected component. Supports Read article
6 min read The Monotonic Stack Pattern A monotonic stack maintains elements in strictly increasing or strictly decreasing order. When a new element Read article
6 min read Feed Architecture Overview A social feed shows users content from people and pages they follow, ranked by predicted engagement. The Read article
5 min read Stack: LIFO and Its Applications A stack (Last In, First Out) is the go-to structure when you need to process Read article
6 min read The Two Pointers Pattern Two pointers uses two indices that move toward each other (or in the same direction) to Read article
