Explore techniques for measuring and optimizing PromQL and MetricsQL expression complexity in this 28-minute conference talk from Conf42 Observability 2024. Delve into the data model used by Prometheus and VictoriaMetrics, understand the concept of time series, and learn when PromQL/MetricsQL queries can become slow. Discover how to assess the number of series and samples a query selects, and understand the distinction between selected and processed samples. Examine the performance impact of various functions and gain insights into performance improvement strategies such as query caching, filter pushdown, and recording rules. Explore how VictoriaMetrics can simplify the optimization process and access additional resources for further learning.