This article provides guidance on sizing DataStax Astra for new or existing Apache Cassandra applications. It explains that the free tier (C10) is a good starting point, and suggests using D10 for time-series or immutable workloads. The article also discusses replication and scalability in Astra, which ensures availability across multiple nodes and availability zones. Users can choose between C and D tiers based on their compute size requirements and storage needs, with storage scaling in increments of 500GB for the C tier and 1.5TB for the D tier. The article concludes by highlighting Astra's features and tools that aim to simplify database management and improve user experience.