Ask HN: What are the details of your CI/CD system?

I'd love to hear more about the CI/CD systems people have put in place at various companies. Would appreciate if people would share:

1) what solutions you're using

2) what security risks you've taken into account if using outside vendors

3) how to take into consideration VPCs and internal/external situations

4) what size company/number of developers you support with this.

Any other information would also be appreciated!