Master Coding Skills &
System Design.

Master browser Web APIs — Fetch with AbortController, localStorage vs sessionStorage, IntersectionObserver for lazy loading, MutationObserver.

Master string searching algorithms — naive O(nm), KMP O(n+m) with failure function, Rabin-Karp with rolling hash, and when to use each.

Understand MySQL replication — binary log, replica setup, replication lag, routing reads to replicas and writes to master in PHP.

Complete PHP security guide — prevent XSS with htmlspecialchars, SQL injection with PDO, CSRF with tokens, and add security headers.

Master caching patterns — Cache-Aside, Write-Through, rate limiting with Redis, sorted set leaderboards, distributed locks, and stampede prevention.

Master JavaScript design patterns — Module (IIFE), Observer (pub/sub), Proxy for intercept, Strategy for algorithm swapping.

Master sliding window and two pointer patterns — fixed and variable windows, two sum with sorted array, remove duplicates, minimum window substring.

Master SQL views as reusable virtual tables, BEFORE/AFTER triggers for automatic reactions, and scheduled events without cron.

Master PHP cURL and Guzzle — GET/POST requests, authentication headers, concurrent requests, and error handling for external APIs.