Mautic

Symfony-based PHP monolith backed by MySQL, relying on cron-driven background workers for campaign execution and email sending rather than a modern queue system by default. Community Docker images exist but require careful cron and worker configuration.

Known to have performance issues at scale — the cron-based campaign engine and PHP monolith architecture don't parallelize well for large contact lists or high email-sending volume without significant infrastructure tuning (dedicated queue workers, MySQL read replicas).

Needs an app pod, MySQL pod (`mysql.pod:3306`), and a scheduled cron/worker process for campaign execution — the cron dependency is the main gotcha since Nexlayer pods need an explicit sidecar or scheduled job mechanism for it rather than relying on host cron. `SITE_URL` must match the Nexlayer `<% URL %>` exactly for tracking pixels and unsubscribe links to work.