I'm using Kea as a DHCP server and I need the service to start on boot. I'm not sure why it doesn't ship with a systemd .service file. Here is the file I ended up using:

# Put this in /etc/systemd/system/kea-dhcp4.service
# Reload systemd so it picks it up `systemctl daemon-reload`
# Enable it on boot: `systemctl enable kea-dhcp4`

[Unit]
Description=ISC KEA IPv4 DHCP daemon
Documentation=man:kea-dhcp4(8)
Wants=network-online.target mariadb.service
Requires=kea-ctrl-agent.service
After=network-online.target mariadb.service mysql.service

[Service]
ExecStart=/usr/sbin/kea-dhcp4 -c /etc/kea/kea-dhcp4.conf

[Install]
WantedBy=multi-user.target

This is borrowed from Skywalker-11.