Master Coding Skills &
System Design.

Complete PHP file handling guide — file_get_contents, fopen streams, secure file upload with MIME type validation, and file system operations.

Design a notification system for billions of daily notifications — Kafka fanout, FCM/APNs workers, user preferences, and exactly-once delivery.

Master JavaScript error handling — built-in error types, custom error classes, async error handling, and global unhandledRejection handlers.

Master greedy algorithms — activity selection problem, fractional knapsack, Huffman coding, and how to prove a greedy algorithm is correct.

Deep dive into SQL transactions — ACID properties explained, all four isolation levels, dirty reads, phantom reads, and savepoints.

Master PHP regex — preg_match, preg_match_all, preg_replace, named groups, lookahead, and a library of common validation patterns.

Design search autocomplete for 10M QPS — Trie in memory, Redis caching, query aggregation pipeline, and personalization layer.

Understand JavaScript modules — CommonJS require/exports vs ES Modules import/export, static vs dynamic loading, and tree shaking.

Build a Trie from scratch — insert, search, prefix matching, autocomplete DFS traversal, and word search with backtracking.