This Zsh service-plugin will run redis-server pointing it to configuration file redis.conf. This can be used with plugin z-shell/zredis to have the redis-backend running, to use shared-variables (between shells). Bind the variables using lazy method (-L {type} option):

# Port 4815, database nr. 3, key "MYLIST"
ztie -d db/redis -f "127.0.0.1:4815/3/MYLIST" -L list mylist

The command ztie is provided by z-shell/zredis plugin.

A service-plugin needs a plugin manager that supports loading single plugin instance per all active Zsh sessions, in background. ZI supports this, just add:

zi ice service'redis'
zi light z-shell/redis

to ~/.zshrc.

First Zsh instance that will gain a lock will spawn the service. Other Zsh instances will wait. When you close the initial Zsh session, another Zsh will gain lock and resume the service. z-shell/zredis supports reconnecting, so all shared-variables will still work.