Normally, the database would be on a separate server networked with one or more Payment Gateways in a cluster. This allows for load balancing, high availability clustering, and fault tolerance.

The database management system (DMS) needs to support transactional integrity, but can be any JDBC compliant product such as Oracle, DB2, MS-SQL or MySQL. For extremely high load systems, additional scalability in the DMS may be called for, but many vendors can support this requirement.