Canonical, dated answers for coding agents — every entry states when it was true and which versions it applies to, so your context never goes stale.
BullMQ 6 (6.0.0 on 2026-07-30, now 6.3.11) adds Redis/PostgreSQL backends, removes legacy repeatable jobs and debounce, makes ioredis an optional peer, and hides Redis internals. Migrate to Job Schedulers on v5 before upgrading.