Azure Blockchain Service is Microsoft's Blockchain-as-a-Service (BaaS) offering that has been available in preview for quite some time. Essentially, it is a fully managed ledger service which allows organizations to manage their blockchain network in Azure, perform network deployments, and develop smart contracts. It currently supports Ethereum Quorum using Istanbul Byzantine Fault Tolerance (IBFT) as its underlying consensus mechanism.
Microsoft has now announced that it will be shutting down Azure Blockchain Service on September 10, 2021.
While no official reasoning has been given regarding why the service is being retired, Microsoft has recommended that customers immediately start looking for an alternative. For solutions which are already in production or pilot phases, the primary suggestion is to migrate to ConsenSys' Quorum Blockchain offering on Azure since that is also a managed service. Alternatively, customers can opt to utilize blockchain resource management templates on their own infrastructure using Azure VMs. Of course, the disadvantage of this approach is that you'll have to manage the solution yourself after deployment.
For new blockchain deployments and planning, Microsoft has recommended the Quorum and Besu templates available in the Azure Marketplace. The company has also highlighted migration and data export steps and strategy in its guidance here.
Existing Azure Blockchain Service deployments will be supported up until September 10, 2021, which is why customers should start evaluating alternatives immediately. New deployments will not be allowed after May 10, 2021.