Cassandra is a great fit for high write use cases, which makes it a popular choice for storing time series and sensor-collection workloads. At Crowdstrike, we've been using Cassandra for just that purpose, collecting petabytes of expiring time series data. In this talk, I'll discuss compaction in time series workloads, and the TimeWindowCompactionStrategy we developed specifically for this purpose. I'll detail TWCS specific configuration properties, some lesser known compaction sub-properties that apply to all compaction strategies, and also cover other general tricks and tuning that are useful for very large time-series workloads.