Troubleshooting Databases: Slow Queries, Deadlocks, Lost Updates | Database Course Ep 31

Why is this query taking 100 seconds? When something goes wrong in a database, the fastest way to the answer is to work layer by layer. This episode gives you a systematic approach to troubleshooting. We start with troubleshooting layers, isolating whether the issue lives in the application, query, engine, storage, or infrastructure. Then we diagnose slow queries using slow query logs, indexes, and execution plans. You'll learn how to spot concurrency problems, including locks and the classic deadlock where two transactions each hold a lock the other needs. We cover data integrity issues like the lost update problem, how isolation levels from READ UNCOMMITTED to SERIALIZABLE affect correctness, and the role of ACID. We look at availability and infrastructure failures such as hardware, power, storage, and network problems, and finish with the DBA checklist: a practical mental model for diagnostics, system health, cloud systems, and security configuration. What you'll learn: A layered approach to isolating database problems Diagnosing slow queries Identifying locks and deadlocks The lost update problem and isolation levels Infrastructure and availability failures A repeatable DBA troubleshooting checklist Chapters: 0:00 Introduction 0:44 Why Flat Files Fail: A Quick Review 1:22 Episode Overview 1:40 Troubleshooting Layers: Isolating the Issue 2:45 Diagnosing Slow Queries 4:47 Concurrency and Deadlocks 6:20 Ensuring Data Integrity: Preventing Wrong Results 8:50 Availability and Infrastructure 10:14 The DBA Checklist: A Practical Mental Model 11:10 Final Question: Which Layer Will You Investigate First? Cybersecurity Masterclass by Joshua Moses | CyberTrace Foundation.