I am doing research in the optimization space with a focus on computer systems, and I am curious to hear from backend engineers/architects/server admins about their optimization/control problems, especially in cloud settings.

What were situations where you wished you had a tool that could optimize/dynamically control x, where x could be anything from your database indexing to the resource provisioning for your analytics workloads? Situations where maybe tuning that particular x would have made a significant dent to your AWS/Azure/Google Cloud bill?

Further, if you are using optimization frameworks such as Spearmint or Hyperopt for parameter tuning, what is missing? If you are not using any of these tools but have looked at them, what would you need in terms of additional utilities or features (e.g. missing language clients/hosted versions/deployment mechanisms) to use one?