Consider using mmdebstrap instead of debootstrap
We are currently using debootstrap to generate our Debian images. We might want to switch to mmdebstrap: https://gitlab.mister-muffin.de/josch/mmdebstrap
It seems using mmdebstrap would make the creation of chroots faster (because of using apt directly, and because security updates do not need to be installed in a separate step). Although we only create one base chroot tarball for each Debian release, so this wouldn't make a significant difference in overall build time.
An other interesting feature is support for Linux user namespaces, allowing the creation of chroot tarball without root access, which could help for legacy/trac#23631 (moved).