Flame graph is way to visualize profiling data that allows the most frequent code paths to be identified quickly and accurately. They can be generated using Brendan Gregg's open source programs on github.com/brendangregg/FlameGraph, which create interactive SVG files to be checked in browser. The source of profiling data does not really matter - it can be perf profiler, bpftrace, Performance Schema, EXPLAIN output or any other source that allows to convert the data into the expected format of comma-separated "path" plus metric per line. Different types of Flame Graphs (CPU, Off-CPU, Memory, Differential etc) are presented. Various tools and approaches to collect profile information of different aspects of MySQL server internal working are presented Several real-life use cases where Flame Graphs helped to understand and solve the problem are discussed.