Choose between EventBridge Scheduler and EventBridge time-based rules for a recurring or one-time task

Steps

1. Use EventBridge Scheduler if per-schedule timezone awareness (including DST handling) is needed — legacy scheduled rules always evaluate in UTC only
2. Use Scheduler's native at() expression for genuinely one-time schedules; legacy rules only support rate()/cron() and require workarounds for one-off runs
3. If more than 5 targets are effectively needed, use Scheduler — each schedule invokes one target but that target can be any of 270+ AWS services via its universal-target mechanism, whereas a rule is hard-capped at 5 targets with no quota increase available
4. For very large numbers of independent schedules (beyond roughly 300 rules per event bus, extendable to 2000), prefer Scheduler, whose default account quota is 10 million schedules per Region
5. Use Scheduler's FlexibleTimeWindow.MaximumWindowInMinutes (1–1440) to jitter invocation times and avoid thundering-herd bursts — legacy rules have no equivalent
6. Configure retry behavior appropriately: Scheduler's RetryPolicy supports MaximumRetryAttempts (0–185) and MaximumEventAgeInSeconds (60–86400), both configurable per schedule with a per-schedule DLQ