Spec a job scheduler that runs on 3 replicas

Your Go service runs scheduled jobs, such as "send the daily digest at 9:00" and "reconcile invoices every hour". It is deployed as 3 replicas for availability. An agent will build the scheduler.

Write the spec you would hand the agent.

What you know:

• each job is defined in code with a cron expression and a time zone, such as 0 9 * * * in Europe/London
• every replica can reach Postgres
• deploys restart the replicas one at a time, a few times a day
• some jobs take up to 20 minutes

Then, in a few sentences: what goes wrong with "run these jobs on a schedule" here?