Explanation:
Box 1: Azure SQL Database single database
Serverless is a compute tier for single databases in Azure SQL Database that automatically scales compute based on workload demand and bills for the amount of compute used per second. The serverless compute tier also automatically pauses databases during inactive periods when only storage is billed and automatically resumes databases when activity returns.
Scenarios well suited for serverless compute
Single databases with intermittent, unpredictable usage patterns interspersed with periods of inactivity, and lower average compute utilization over time.
Single databases in the provisioned compute tier that are frequently rescaled and customers who prefer to delegate compute rescaling to the service.
New single databases without usage history where compute sizing is dificult or not possible to estimate prior to deployment in SQL Database.
Box 2: Azure SQL Managed Instance
Azure SQL Managed Instance is the intelligent, scalable cloud database service that combines the broadest SQL Server database engine compatibility with all the benefits of a fully managed and evergreen platform as a service.
Box 3: Azure SQL Database elastic pool
Azure SQL Database elastic pools are a simple, cost-effective solution for managing and scaling multiple databases that have varying and unpredictable usage demands. The databases in an elastic pool are on a single server and share a set number of resources at a set price. Elastic pools in SQL Database enable software as a service (SaaS) developers to optimize the price performance for a group of databases within a prescribed budget while delivering performance elasticity for each database.
Reference:
https://docs.microsoft.com/en-us/azure/azure-sql/database/serverless-tier- overview?view=azuresql
https://docs.microsoft.com/en- us/azure/azure-sql/database/elastic-pool-overview?view=azuresql
https://docs.microsoft.com/en-us/azure/azure-sql/managed-instance/sql- managed-instance- paas-overview