It's probably worth spending some time exploring why you might choose to use Cosmos rather than one of the myriad other database engines. There are two questions here: why cloud, and why Cosmos specifically?
Benefits of using Cosmos DB
Why cloud? It's Microsoft's job to scale – not yours
Because Cosmos DB is managed by Microsoft, transitioning to it means that there are suddenly some things that you don't need to worry about. For example, have you ever tried to configure SQL Server to fail over, or what about if you're located in the US and your customers are in Australia? Cosmos handles all these scenarios for you on a pay-as-you-go arrangement. Obviously, if you want your data replicated on...