Your application stores user-specific state information in a MySQL database, causing schema maintenance issues. What storage option should be used instead?

Using Cloud Datastore or Firestore is advantageous for applications that store user-specific state information because these databases are designed for flexible, schema-less storage. This characteristic allows you to handle varying types and structures of data without the need for rigid schemas typically associated with relational databases like MySQL.

Cloud Datastore and Firestore enable a more agile development process since they support hierarchical data models and automatic scaling, making it easier for applications with user-specific data to adapt as requirements evolve. With features like strong consistency and built-in support for transactions, they provide a user-friendly environment that can easily accommodate dynamic data without the overhead of schema migrations or maintenance issues.

In contrast, the other options present challenges for this specific use case. Cloud SQL, while a powerful relational database service, still requires schema management and may lead to the same maintenance issues that prompted the consideration of an alternative. Cloud Storage is primarily used for unstructured data and file storage rather than structured or semi-structured database needs. Cloud Spanner, although it offers horizontal scalability for relational data, can also involve complex schema management and may be more than what is necessary for applications focused on simple user state information.