8 min read Core Pattern Tree DP follows a single structural pattern: post-order DFS. You recurse into children first, then compute the answer […] Read article
8 min read Core Concepts A stock exchange at its core is a system that matches buyers and sellers. The central data structure Read article
10 min read Linked list problems trip up candidates because pointer manipulation is easy to mess up under pressure. These patterns cover every Read article
10 min read Message queues like Kafka, RabbitMQ, and SQS show up in both system design and low-level design interviews. Understanding the internals Read article
10 min read Sorting problems appear constantly in interviews – not just “implement merge sort” but as tools to simplify harder problems. Master Read article
7 min read Requirements Functional requirements for a URL shortener: Create a short URL from a long original URL Redirect users from the Read article
8 min read When Greedy Works: The Exchange Argument Greedy algorithms make the locally optimal choice at each step. They are provably correct Read article
9 min read Payment State Machine A payment must move through well-defined states. Never allow arbitrary transitions or skipped states. INITIATED -> PROCESSING Read article
12 min read Caching is the single highest-leverage optimization in most systems. A well-designed cache can cut database load by 90% and reduce Read article
9 min read Search autocomplete is one of the most latency-sensitive features in any product. Users expect suggestions within 100ms of each keystroke. Read article
9 min read Strings appear in roughly 25-30% of coding interviews. Unlike arrays or trees, string problems have a concentrated set of patterns Read article
8 min read Rate limiting is a core system design topic. This guide covers every major algorithm, their trade-offs, and Redis implementation patterns Read article
7 min read Interval problems are a reliable interview topic at every level. The core patterns repeat across dozens of problems – learn Read article
9 min read Trie (prefix tree) problems appear frequently in coding interviews. This guide covers the core patterns with Python implementations you can Read article
11 min read Authentication is one of the most common low-level design questions in system design interviews, and one of the most commonly Read article
