resque-scheduler

Jobs are not executed exactly at the scheduled time; the scheduler polls at intervals (default 5 seconds), meaning there can be delays, as admitted in the delayed jobs section where it states jobs fire after the time has passed.

Requires careful setup with Rake tasks, environment variables, and optional dynamic scheduling enablement, which can be error-prone for new users, as shown in the installation and configuration examples.

Tightly coupled with Resque and Ruby, making it unsuitable for projects using other job queues or polyglot architectures, and it adds dependencies on Redis and specific gem versions.

If the scheduler process is down, missed scheduled jobs are not recovered upon restart, unlike delayed jobs, which can lead to gaps in periodic tasks, as noted in the redundancy section.