I think it's often a better strategy to do sharding or micro-services and if possible keep the service so small that it's state can fit in a single machine. If you can have data boundaries, like for example one customer do not need to access the data of another customer, then you can separate customers's data and place them in different databases.
Sharding your product so that no cross-shard links are possible is robust and scalable, but it requires you to understand your final product very well at design time. If you start down that path and then bolt on some cross-shard data, the end result is almost always worse then if you had planned for that from the start.