This document summarizes Rahul Kumar's talk on composing and scaling data platforms. It discusses how the tools software engineers use shape the software that is built. It also explains how databases affect how developers treat state and mutability. The talk highlights how data platforms range in complexity from caching layers to integrated data pipelines. It discusses composing platforms through concepts like data representation, parallelism, and architecture. Sequential data access and streaming are more efficient than random access. Parallelism and distributing work across servers can scale platforms.