The last way to scale your database is to use sharding. As opposed to elastic pools, by using sharding you allocate individual resources to each of your databases. It is also one of the models for horizontal scaling (so you rather provision another database than scale up your existing one).
Note that you can use sharding also for elastic pools by using the Elastic Database split-merge tool: https://docs.microsoft.com/en-us/azure/sql-database/sql-database-elastic-scale-overview-split-and-merge.
In general, you will use sharding if you:
- Have too much data to be able to handle it with an individual instance
- Want to load-balance requests
- Want to geo-distribute your data
The important thing here is the requirement that the data structure ...
