Question

An order-state worker consumes an SQS FIFO queue, partitioned by `MessageGroupId = order_id` so each order's events process in order. At 10:15 a subset of orders stop advancing — their later events never process — while most orders are fine. Dashboards: `ApproximateNumberOfMessagesVisible` is flat-ish, but a few message groups show messages stuck and the worker logs an unhandled exception on one message that keeps reappearing after the visibility timeout. No DLQ is configured. How do you triage, unblock the stuck orders, and harden the consumer?