At irax we’ve been building systems for quite some time now, we started off by writing software to switch on TV channels on the Sky service. Followed closely by creating a custom Customer Resource Management systems ( CRM) especially to handle the requirments for TV channels.
We’ve also created our own service for storing and processing payment cards that met the stringent criteria set by the Payment Card Industry Digital security standard ( PCI/DSS) and customers using this system have achieved PCI/DSS level one compliance.
Our technology implementations rely on open source, so we have used that to create all our systems. Originally in Local Datacentres. Now that experience is used in implementing systems in the cloud , especially AWS.