Azure sync service to enable Hybrid applications

SQL Data Sync is a service built on Azure SQL Database that lets you synchronize the data bi-directionally across multiple databases, both on-premises and in the cloud.

Data Sync uses a hub and spoke topology to synchronize data. You define one of the databases in the sync group as the hub database. The rest of the databases are member databases. Sync occurs only between the hub and individual members.

• Sync Metadata Database contains the metadata and log for Data Sync. It can be created in any resource group or server within the same subscription and region as that of Hub database.
• Member database can be in any subscription, region or resource group.
• 1433 port (outbound) being open is one of the prerequisites for the sync process to work.
• The SQL Data Sync service communicates with SQL Server databases via the client agent. This security feature prevents direct communication with databases behind a firewall.
• Data Sync provides two options for conflict resolution, Hub wins or Member wins.

Very important considerations:

1. Hub database must be an Azure SQL Database.
2. Azure SQL Data Sync does not support Azure SQL Managed Instance at this time.
3. Sync Metadata Database has to be an Azure SQL Database located in the same region as the Hub Database. You can only have one Sync Metadata Database per region and subscription.
4. Install the on-prem Sync agent on a server that isn’t the SQL server database server.
5. Install the Sync agent by using the least privileged user account that has network service access.
6. Multiple on-prem databases can be registered with one Sync agent. But, don’t register one on-prem database with multiple Sync agents.

When to use or not use:

Disclaimer: The posts here represent my personal views and not those of my employer or any specific vendor. Any technical advice or instructions are based on my own personal knowledge and experience.