Master Coding Skills &
System Design.

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.

Fix slow MySQL queries — enable slow query log, read every EXPLAIN field, identify full table scans, filesorts, and apply targeted fixes.

Master PHP 8.x type system — union types, enums with methods, named arguments to skip optional parameters, and intersection types.

Design a video streaming service for 238M subscribers — transcoding pipeline, adaptive bitrate HLS, CDN architecture, and segment caching.

Master JavaScript generators — function*, yield, yield*, two-way communication, infinite sequences, and custom iterators with Symbol.iterator.

Master Python heapq — min-heap, max-heap simulation, Top K elements pattern, merge K sorted arrays, and Dijkstra with priority queue.