Day - 6 | Write-Ahead Logs (WAL) Explained: The Secret Behind Fast Database Writes

How do databases recover after a crash while maintaining data durability? In this video, we explore **Write-Ahead Logging (WAL)**, a fundamental concept in database internals and system design. Write-ahead logging can improve database write performance by converting many expensive random data-page writes into more efficient sequential log writes. Instead of immediately updating data scattered across disk, changes are recorded in a log first. The database can then use this log to support crash recovery and maintain durability guarantees. Welcome to *Day 6 of the Backend Interview Preparation Series* on Hello Backend! In this video, we'll break down WAL using simple diagrams, step-by-step explanations, and practical examples. 📚 What You'll Learn What is Write-Ahead Logging (WAL)? Why databases use a write-ahead log How sequential log writes work How WAL supports database write performance How the WAL flush process works How databases recover after a crash The relationship between WAL, database pages, and durability Why WAL is important for database internals and system design interviews 🎯 Who Should Watch? Backend developers preparing for SDE-1, SDE-2, and SDE-3 interviews Software engineers learning database internals Developers preparing for system design interviews Anyone interested in database performance, durability, and crash recovery 🚀 About Hello Backend Welcome to Hello Backend! I create videos about software engineering, backend development, databases, distributed systems, and system design interview preparation. Subscribe to learn complex backend concepts through simple explanations, practical examples, and interview-focused lessons. If you find this video helpful, please like it, share it with fellow developers, and subscribe to Hello Backend for more backend engineering tutorials. #WriteAheadLogging #WAL #DatabaseInternals #SystemDesign #BackendInterview