Master Coding Skills &
System Design.

Master load balancing — round robin, weighted round robin, least connections, IP hash sticky sessions, and L4 vs L7 load balancers.

Master JavaScript regex — test/match/replace/exec methods, named groups, lookahead/lookbehind, and validation pattern library.

Master backtracking — the framework (choose, explore, unchoose), N-Queens problem, Sudoku solver, generate all subsets and permutations.

Master MySQL JSON columns — INSERT, JSON_EXTRACT, JSON_SET, JSON_ARRAYAGG, and indexing JSON paths via generated columns.

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.