Configuration settings for management server and proxies are stored in the management server Configuration Database located at C:\ProgramData\Veeam\Backup365\ConfigDB on that server. Database structure is accessed and managed using the ESE engine.
Configuration data is periodically replicated to proxy servers for consistency and stored to the proxy server Configuration Database located at: C:\ProgramData\Veeam\Backup365\ProxyDb. Proxy settings are stored in the Proxy.xml file in the same folder.
Since each management server also hosts the default proxy, the corresponding database can be found on the management server, too - at C:\ProgramData\Veeam\Backup365\ProxyDb.
When a job is executed on the proxy server, its session data is also stored to that proxy’s Configuration database. This information is periodically synchronized (replicated) with the management server.