In this chapter, we discussed the non-functional requirements for data storage solutions. It has become clear that a data lake, which is an evolution of a data warehouse, consists of multiple layers that have their own requirements and thus technology. We have discussed the key requirements for a raw data store where primarily flat files need to be stored in a robust way, for a historical database where temporal information is saved, and for analytics data stores where fast querying is necessary. Furthermore, we have explained the requirements for a streaming data engine and for a model development environment. In all cases, requirements management is an ongoing process in an AI project. Rather than setting all the requirements in stone at the start of the project, architects and developers should be agile, revisiting and revising the requirements after every iteration.