15. Asynchronous Systems and Back Pressure

Episode 15 of 34 | System Design: From Fundamentals to Interview Mastery An original video-processing workflow explains durable job acceptance, queues versus logs, at-least-once delivery, idempotent effects, ordering, visibility leases, poison jobs, retry budgets, dead-letter handling and back pressure. It distinguishes accepted work from completed work and models recovery explicitly. Original script, worked examples, diagrams and animation. Adapted educational presentation; no endorsement implied. Voice generated locally with the speaker's authorization. Chapters 0:00 Welcome and what we will cover 0:11 Accepted is not the same as completed 1:26 Publish work without losing the durable job 2:51 A worker crash can cause repeated delivery 4:17 Visibility leases and ordering constrain concurrency 5:40 Retries and poison jobs need a stopping rule 7:03 Back pressure bounds the amount of promised work 8:22 A queue and an event log have different consumption models 9:47 Operate the job lifecycle, not just the queue depth 11:15 Recap, practice and thank you