System Design Card 403 — Queues and Async Processing / Structure
Concern
Async pipelines absorb bursts, decouple components, and isolate slow or failure-prone downstream work. Notification sending, video processing, and search indexing often belong off the synchronous request path.
What Structure means for this concern
In BASIC, the Structure step is where you turn the chosen trade-offs into a clear high-level architecture and request flow. For Queues and Async Processing, that means the candidate should make this concern visible at the right moment instead of bolting it on at the end.
Design move
A good move is to make the plan visible before full execution. Tie the concern back to the user flow, the workload, and the dominant trade-off. That keeps the design grounded and makes it easier for the interviewer to follow why a cache, queue, replica, partition, or rate limiter is actually necessary.
Common miss
The miss is keeping everything synchronous and then trying to explain away latency and spikes later. BASIC helps because the staged flow keeps this concern proportional to the prompt and connected to the rest of the architecture.
BASIC prompt
“When I reach the Structure stage, how does Queues and Async Processing change the architecture, the trade-offs, or the review checklist?”