We do it from the core infrastructure we run ourselves. Built the full stack to have flexibility and innovate in industry where 90+% of CC transactions still run on mainframes & COBOL
Traditionally, we do it this way too, these piece of the payments ecosystem are all whitelisted IPs for access and MPLC circuits for connections.
So its 2/3rds BD to get setup, 1/3 enterprise engineering and a lot of integration work to get fully setup and running. Payments is the only trillion dollar industry where nothing is written down, we're working on changing that since we find a lot of the stories fascinating and so do most people we retell them to.
If anyone is in Oakland area and wants a primer, always happy to share, we spent 3 years learning industry and now its our time to start giving back.