We use Amazon Web Services in Ireland for core hosting services. See AWS Security whitepaper for details. https://d0.awsstatic.com/whitepapers/Security/Intro_to_AWS_Security.pdf.
Other frequently asked technical questions include:
Can this integrate with my VMS?
Can this integrate with my current ERP or ATS?
Can I add other employees, like contractors?
Can I host this on my infrastructure?
Can I apply my organisation's branding?