Common practices to determine what database technology to use [closed]

Adding a no-answer as I don't know of a formal method for choosing a database architecture (remember you buy a architecture with special backup requirement, HA feature, hardware requirements). Basically it boils down to

• You need the optimal database for the enterprise not only your project (If a "optimal" database for your project would be DB2 on AIX is of no use to your project if all your operating team does only Windows and SQL Server)
• Do you need HA? which one? Switchover? active-active?
• What type of disaster recovery do you need?
• Formal (e.g. customer requirements, supported OS) and legal requirements
• What type of infrastructure is on the customer site (SAN? virtualization? cloud?)
• Monitoring? Backup? (If your backup software does not support a RAC database or the modules for backing it up cost more than the rest of your project, it's pointless to use that database. Same is valid for monitoring
• Skill of your operating teams
• type of data (Geodata?) Is it business critical? (your HR has slightly different impact than a simple database the tags on your website
• amount of data

There is a whole lot more to consider but in my experience these are good starting points.